3.1V.%..2 L. .. .. rddkhwmfirh. «a .. TE, 9.:- ..5 d3 L5» e.» .«F 6:? .. 3,” my". «,2, Wm . n . $.73: 8. $3.51.“: . .w. —fii1 A p ,. £3 ”Hafiz—F. n... 5w. .5“ a "may.” ‘ . .2? 2.... 41A . . . ... 14.2 23. a. . Amrwmmmm . . s . «.9. I 53.3“». . >1.qu- ’ I. t r v.3. Ky? 1:51.." .1 up. . .Q ..< 2.. , x . L ...I .3: .1. v f :5 s m. "my: 3.. :u. , . a3a_::x 52.3. . f . v «a? awmkiz. A I. :3. .nz. . t a z... he“... This is to certify that the dissertation entitled DIPOLE ALIGNMENT VIA PHASE SEPARATION OF AMPHIPHILIC SIDE CHAINS presented by Gao Liu has been accepted towards fulfillment of the requirements for Ph.D. degree in Chemistry 5‘ Major professor Date /9 Mfr/l 200/ MS U is an Affirmatiw Action/Equal Opportunity Institution 042771 LIBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 cJCIRC/DateDuopeb-nm DIPOLE ALIGNMENT VIA PHASE SEPARATION OF AMPHIPHILIC SIDE CHAINS By Gao Liu A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 2001 ABSTRACT DIPOLE ALIGNMENT VIA PHASE SEPARATION OF AMPHIPHILIC SIDE CHAINS By Gao Liu Polymeric 2“d-order nonlinear optical (NLO) materials require a nonisotropic array of noncentrosymmetric molecules. This is achieved in practice by aligning molecules with strong dipoles in a matrix, usually by poling using an electric field. The high molecular dipole moment hinders macroscopic alignment of chromophores, because electrostatic intermolecular interactions can extend over considerable distances (>1nm) and favor the formation of antiparallel alignment of dipoles. Electrostatic interaction energies can exceed thermal energies to favor an overall centrosymmetric ordering of chromophores. We investigated whether the tendency for phase separation seen in diblock oligomers can be used to align chromophores and produce thermodynamically stable 2"“- order NLO materials. We synthesized a series of exact length diblock oligomers with alkyl and ethylene oxide chains attached at the one and four positions of a phenyl ring. DSC, Raman and FF-IR experiments indicated a stepwise crystallization mechanism for these series of compounds. Powder X-ray diffraction data show that they adopt a lamellar structure with the benzene rings aligned in a planar array at the interface due to phase separation of the alkyl and ethylene oxide chains. The lamellar structure changes upon annealing at higher temperatures, often forming interdigitated structures. NLO chromophores could be aligned by the same approach. The benzene ring of the oligomers was replaced by p-nitroaniline since its size is close to that of benzene. The molecules crystallized in a head-to-tail array of chains due to strong H-bonding between amino hydrogens and the neighboring oxygens of the nitro group. For the case of short chains, the molecules pack in layers in an antiparallel fashion due to the strong dipole- dipole interaction, effectively canceling the net dipole moment of the crystal. Electrostatic effects favor pairing of the dipole moments, while phase separation and crystallization of the ethylene oxide and alkyl blocks favors alignment of the dipoles. The competition of these two energy terms determines the final structures of the compounds. When the amphiphilic chains are sufficiently long, the effects of phase separation dominate and the dipole moments are aligned at the interface between the Side chains. Thus, manipulating the phase behavior of the block copolymers opens a new route to materials with ordered dipoles. To my family and Yushuang. iv ACKNOWLEDGMENTS I wish to express my deep appreciations to my advisor — Professor Gregory L. Baker for his guidance, patience and constant encouragement throughout the course of this research. When I first joined the Baker Group, I knew very little about polymer science. Thanks to his efforts, I graduate as a polymer chemist. He is a good mentor in all aspects. What I have learned from him is far beyond chemistry itself, and it will continue influence me in the future. I also like to express my gratitude to Professor James E. Jackson, Gary J. Blanchard, William H. Reusch and Thomas J. Pinnavaia, who gave me great help during the years of my graduate study and offered critical insights on my dissertation work. Many thanks go to all Baker Group members, who helped me and made my experience at MSU enjoyable. Thanks also go to Pam who hosted the wonderful summer and Christmas parties at Baker’s ranch every year. I want to thank my girl friend Yushuang who is making me a better person all the time. I thank my parents, my brother and sister in law for their constant love and support r during the past years. TABLE OF CONTENTS List of Abbreviations ............................................................................. ix List of Figures ..................................................................................... x List of Schemes .................................................................................... xv List of Tables ....................................................................................... xvi CHAPTER 1. Introduction ....................................................................... 1 1.1 Amphiphilic Materials .................................................................. l 1. Categories of amphiphiles ........................................................... 4 2. Properties of amphiphiles .......................................................... 12 1.2 Diblock Copolymer Phase Behavior .................................................. 20 1.3 Nanometer-Scale Ordered Materials .................................................. 22 1. Diblock copolymer phase separation ............................................... 25 2. Amphiphiles and colloidal assemblies ............................................. 27 3. Liquid crystal assemblies ............................................................ 27 1.4 References ................................................................................. 31 CHAPTER 2. Thermal and Structural Properties of Amphiphilic Diblock Oligomers.. 34 2.1 Introduction ............................................................................... 34 2.1 Results ..................................................................................... 42 1. Materials synthesis .................................................................... 42 2. Properties of C,PhEO,C1 ............................................................ 47 2.3 Discussion ................................................................................. 74 1. Conformation and solid-state structure ............................................. 74 2. Stepwise crystallization .............................................................. 78 vi 3. Effects of annealing on structure ..................................................... 89 2.4 Conclusions ................................................................................ 93 2.5 References ................................................................................. 94 CHAPTER 3. Dipole Alignment via Phase Separation of Amphiphilic Side Chains 97 3.1 Introduction ................................................................................ 97 l. Origins of 2"d-order NLO effects in organic chromophores ..................... 100 2. Noncentrosymmetn'c arrays of chromophores ...................................... 104 3.2 Results ...................................................................................... 110 1. Material synthesis ..................................................................... 110 2. Properties of CxPhNEoyCl .......................................................... 118 3.3 Discussion .................................................................................. 133 1. Transformation from paired structures to lamellar structures .................... 133 2. Paired structure of CloPNACm ...................................................... 143 3. H-bonding in the crystal structure of CxPhNEoyCl .............................. 147 3.4 Conclusions ................................................................................ 156 3.5 References ................................................................................. 157 CHAPTER 4. Experimental ...................................................................... 161 4.1 General details ............................................................................ 161 4.2 Compound identification numbers (ID) ............................................... 162 4.3 Material synthesis ........................................................................ 165 1. Synthesis of monotosylated polyethylene glycols ................................. 165 2. THP protection of monotosylated polyethylene glycols .......................... 166 3. THP protection of polyethylene glycol monomethyl ethers ..................... 167 vii 4. Deprotection of polyethylene glycol monomethyl ethers ....................... 168 5. Synthesis of tosylated derivates of polyethylene glycol monomethyl ethers. 169 6. Coupling of alkyl chains to benzene ring ......................................... 170 7. Synthesis of 4-alky1phenols ........................................................ 171 8. Synthesis of CxPhEoyCl ........................................................... 172 9. Nitration of alkylphenol ............................................................. 180 10. Attachment of the CIEOy chain ................................................... 182 11. Reduction of nitro to amino groups ............................................... 184 12. Protection of aniline ................................................................ 185 13. Nitration of protected anilines ..................................................... 187 14. Deprotection of aniline derivatives to give CxPhNEOyCl ................... 189 15. Dimethylation of aniline ........................................................... 191 16. Synthesis of didecyl substituted p-nitroaniline ................................. 192 4.4 References ............................................................................... 194 viii CIOPNACIO CMC CNA CKEOy C,E0,C, CxPhEchr CxPhNCzEOyCI CxPhNEOyCl (1 DNA DSC E E0 H-bonding HRMS IR LB LC LLC m mp NLO LIST OF ABBRIVIATION S See page 111 Critical micelle concentration 2-chloro-4-nitroaniline See page 39 See page 39 See page 43 See page 111 See page 111 Doublet Deoxyribonucleic acid Differential scanning calorimetry Electric field Electro-optical effect Hydrogen-bonding High resolution mass spectrometry Infrared spectroscopy Langmuir-Blodgett Liquid crystal 1yotropic liquid crystal Multiplet Melting point Nonlinear optical Nuclear magnetic resonance Number of repeating units in polystyrene Polyethylene Polyethylene oxide Poly(ethylenepropylene) Poly(p-phenylene vinylene) Polystyrene-block-polyisoprene Singlet Second harmonic generation Triplet Glass transition temperature Melting point X-ray diffraction Chemical shift Free energy change Enthalpy change Entropy change Diffraction angle Wavelength Dipole moment Flory-Huggins parameter ix Figure 1.1. Figure 1.2. Figure 1.3. Figure 1.4. Figure 1.5. Figure 1.6. Figure 1.7. Figure 1.8. Figure 1.9. Figure 1.10. Figure 1.11. Figure 1.12. Figure 1.13. Figure 1.14. Figure 1.15. Figure 1.16. Figure 2.1. Figure 2.2. LIST OF FIGURES Structure of an amphiphilic molecule .......................................... 1 Mechanism for dissolution of solute in solvent ............................... 3 Dispersion of oil droplets into aqueous solutions of surfactant ............. 5 Aggregation of phosphoglycerides into the lipid bilayer that comprises cell membranes ................................................... l 1 Aggregation of amphiphiles at interfaces ...................................... 12 Surface tension of surfactant solutions versus concentration ............... 13 Effective head and chain group areas in surfactants .......................... 14 Structures of micelles in dilute solution (A) and concentrated solutions (B, C) ................................................................... 15 Layered structures of lamellar shaped amphiphiles ........................... 17 Solid state head-to-tail bilayer structure of the monohydrate of l-lauroyl- 1 ,3-propanediol- l -phosphocholine .................................. 1 8 Interdigitated packing structures ................................................. l9 Monolayer crystal structure of N-dodecanoyl-N-methylglucamine. . .1 20 Phase behavior of diblock polystyrene-block—polyisoprene (PS-PD ....... ‘ 23 2-Chloro-4-nitroaniline and polystyrene—block-polyethylene oxide complex ..................................................................... 26 Synthesis of PPV nanocomposites with hexagonal symmetry using polymerizable 1yotropic liquid crystals .................................. 29 Molecular structure of the rod-coil diblock copolymer and schematic illustration of its hierarchical self-assembly into ordered microporous materials .................................................. 30 Surfactant DNA complexes ...................................................... 35 Amphiphiles and tripeptide modified amphiphile complexes ............... 37 Figure 2.3. Figure 2.4. Figure 2.5. Figure 2.6. Figure 2.7. Figure 2.8. Figure 2.9. Figure 2.10. Figure 2.11. Figure 2.12. Figure 2.13. Figure 2.14. Figure 2.15. Figure 2.16. Figure 2.17. Figure 2.18. Figure 2.19. Figure 2.20. Figure 2.21. Figure 2.22. Figure 2.23. Figure 2.24. The structure of C,EO, ......................................................... 41 C,EO,C,, a molecule with a helical ethylene oxide core .................. 42 DSC heating scans of CuPhEoyCl .......................................... 49 DSC heating scans of CmPhEoyCl ........................................... 50 DSC heating scans of CrgPhEOyCl .......................................... 51 DSC heating scans of CzoPhEoyC; .......................................... 52 DSC cooling scans of CuPhEoyCl .......................................... 53 DSC cooling scans of CmPhEoycl .......................................... 54 DSC cooling scans of ClsPhEchl .......................................... 55 DSC cooling scans of CzoPhEoyCl .......................................... 56 Major types of thermal transitions seen in DSC scans ..................... 57 Melting point and heat of fusion as measured by DSC ..................... 58 Comparison of annealed and quenched DSC heating scans Of C [sphEOyCI .................................................................. 61 Comparison of annealed and quenched DSC heating scans of CzoPhEchl .................................................................. 62 Major types of DSC thermal transitions seen in annealed samples. 63 Low angle XRD data for CuhEOyCl ......................................... 65 Low angle XRD data for CmPhEoyCl ....................................... 66 Low angle XRD data for CrgPhEoyCr ....................................... 67 Low angle XRD data for CzoPhEoyC, ...................................... 68 Low angle XRD data for annealed CmPhEchl ........................... 70 Low angle XRD data for annealed CzoPhEOyCr ............................ 71 Raman spectra of CzoPhEoyCl ............................................... 72 xi Figure 2.25. The conformation of CzoPhEoyCr ............................................ 75 Figure 2.26. d-Spacings of CxPhEOy vs.C1EOy length ................................... 77 Figure 2.27. The lamellar structure formed by bilayer packing of CzoPhEO7C1 ....... 78 Figure 2.28. The DSC scans of CzoPhEosCl at various temperatures ................... 80 Figure 2.29. IR spectra Of CzoPhE05C1 ............................. 81 81 Figure 2.30. Stepwise crystallization of CzoPhEosCl ..................................... 82 Figure 2.31. Alkylbenzene weight fraction vs. heat of crystallization for CmPhEoyCl (A) and CzoPhEOyCl (O) ..................................... 85 Figure 2.32. Stepwise crystallization of CzoPhEOsCl ..................................... 86 Figure 2.33. Melting points of the CzoPhEoyCr series of compounds .................. 87 Figure 2.34. Melting points of the C,8PhEo,c. series of compounds .................. 88 Figure 2.35. Raman spectra of CzoPhEosCr ............................................... 90 Figure 2.36. A fully interdigitated packing structure of CzoPhEO7Cr ................... 92 Figure 3.1. The major types of 2"d-order nonlinear optical (NLO) effects ............. 98 Figure 3.2. A) Plots of the electric field of an applied light wave and the induced polarization wave as a function of time for a 2"d-order NLO material; B) Diagram depicting the charge distribution and the polarization in the material as a function of time ................... 101 Figure 3.3. The asymmetric induced polarization can be decomposed into a direct current (DC) component and components at the fundamental and second harmonic frequencies ......................... 102 Figure 3.4. Electric field poling of guest-host system .................................... 105 Figure 3.5. Schematic of layer by layer construction of aligned chromophores by the Langmuir-Blodgett technique ........................ 108 Figure 3.6. P21/c space group of the p-nitroaniline unit cell and the antiparallel arrangement of the paired structural unit ....................... 109 Figure 3.7. Unit cell structure of ClPhNEOoCr ........................................... 120 xii Figure 3.8. Figure 3.9. Figure 3.10. Figure 3.11. Figure 3.12. Figure 3.13. Figure 3.14. Figure 3.15. Figure 3.16. Figure 3.17. Figure 3.18. Figure 3.19. Figure 3.20. Figure 3.21. Figure 3.22. Figure 3.23. Figure 3.24. Figure 3.25. Figure 3.26. Figure 3.27. Unit cell structure of CzPhNEOoCl ......................................... 121 Paired solid state structure of CrPhNEOoCl and CzPhNEOoCr ....... 122 Solid state structure of CyPhNEOzCl ...................................... 123 Powder XRD of the CgPhNEOyCl series of compounds ................ 124 Mid-IR spectra of CxPhNEoyCr ............................................ 126 IR spectra of the N-H stretching region for CxPhNEoycl .............. 127 DSC melting transitions of CxPhNEoyCl ................................. 130 Melting points of CgPhNEOyCr versus numbers of carbon atoms in the ethylene chain ................................................... 131 The p-nitroaniline subunit showing the relative alignment of the dipole moments in the paired structures ................................ 134 Low angle powder XRD of CMPhNEOsCl and annealed CuPhEOsCr .................................................................... 136 Low angle powder XRD of ClgPhNE06C1 and annealed CmeE05C1 ................................................................... 137 Low angle powder XRD of CzoPhNEO-yCl and annealed CzoPhE07C1 .................................................................... I38 Schematic drawing of the CxPhNEoyCl solid state structure ........... 139 The theoretical calculation of dipole-dipole interaction energies ....... 141 IR spectra of CmPNAClo and p-nitroaniline in N-H stretching region ............................................................................ 144 Proposed solid state structure of CmPNAClo .............................. 145 Powder XRD of CloPNAClo and p-nitroaniline ........................... 146 H-bonding arrangements in ClPhNEOoCl ................................ 149 H—bonding interactions in CzoPhNEO7C; .................................. 150 Wlde angle pOWdCI‘ XRD Of CzoPhNEO7C1 and CzoPhNC2E07C1.. . 152 xiii Figure 3.28. Low angle powder XRD of CzoPhNEO7C1 and CzoPhNMeEO-ICIM. 153 Figure 3.29. Powder XRD of C14PhNE05C1 and C14PhNMeE05C1 .................. 154 Figure 3.30. DSC heating scans of CzoPhNMeEO7C1, CzoPhNEO7C1 and an annealed sample of CzoPhEO-yCl ......................................... 155 xiv LIST OF SCHEMES Scheme 1.1. Early method for manufacturing soap .......................................... 5 Scheme 1.2. Procedures for the synthesis of two ethylene oxide- based nonionic surfactants ...................................................... 10 Scheme 2.1. The molecular structures of C,,EOy and CxEOyCx ............................ 39 Scheme 2.2. Example of the acronyms used for naming compounds ...................... 43 Scheme 2.3. Synthesis of exact length of ethylene glycol monomethylethers ............ 44 Scheme 2.4. Synthesis of C,PhEO,C1 ......................................................... 46 Scheme 3.1. Examples of acronyms for compounds ......................................... 111 Scheme 3.2. Synthetic route to CxPhNEOyCl ............................................... 113 Scheme 3.3. Synthetic route to dimethylated CxPhNConyCr ............................ 114 Scheme 3.4. Synthetic route to CroPNACm .................................................. 115 XV LIST OF TABLES Table 1.1. Categories of surfactant and functional groups ............................... 7 Table 2.1. Combinations of ethylene glycol and monomethylated ethylene glycol used in synthesis of CIEOy (y = a + b) ..................... 45 Table 2.2. Overall yields and boiling points of CIEOy at 40 mtorr .................... 45 Table 2.3. Composition of the ethyl acetate/hexane elution system used for purification of C,PhEO,C1 by column chromatography ................ 47 Table 2.4. Melting points and heats of fusion of CrgPhEOy from DSC measurements ..................................................................... 59 Table 2.5. Melting points and heats of fusion of CzoPhEOy from DSC measurements ..................................................................... 60 Table 2.6. Calculated X-ray d-spacings for CxPhEOr Samples were cooled from the melt and held at room temperature for ten to twenty hours before analysis ................................................. 69 Table 2.7. Calculated X-ray d-spacings for CxPhEoy. Samples were annealed at 2 °C below their melting points for two to ten hours until they reached their ultimate structures ............................ 72 Table 2.8. Low angle XRD d—spacings and Hyperchem calculated molecular length of CzoPhEOy series of compounds ....................... 76 Table 2.9. Alkylbenzene weight fractions and heats of crystallization for the CmPhEOy and CzoPhEOy series ...................................... 84 Table 3.1. Purification conditions, yields and physical properties of CxPhNEOyCl ..................................................................... 1 16 Table 3.2. Average d-spacing for the CxPhNEoyCr series of compounds calculated from powder XRD ................................................... 125 Table 3.3. Torsional angles of the side chains in C7PhNEOz .......................... 128 Table 3.4. Melting points and heats of fusion of the CxPhNEOy series of compounds ..................................................................... 132 Table 4.1. Compound IDs for 1 (Scheme 2.3) ............................................ 163 xvi Table 4.2. Table 4.3. Table 4.4. Table 4.5. Table 4.6. Table 4.7. Table 4.8. Table 4.9. Compound IDs for 2 (Scheme 2.3) .......................................... 163 Compound IDs for 3 (Scheme 2.3) .......................................... 163 Compound IDs for 4 (Scheme 2.3) .......................................... 163 Compound IDs for 5 (Scheme 2.4) .......................................... 163 Compound IDs for 6 (Scheme 2.4) .......................................... 163 Compound IDs for 6 (Scheme 2.4) .......................................... 164 Compound IDS for 8 (CxPhEOyCr) (Scheme 2.4) ........................ 164 Compound IDS for 9-15 (Scheme 3.2 & 3.3) ............................... 164 xvii CHAPTER 1 Introduction 1.1 Amphiphilic Materials The term amphiphilic describes molecules that love both aqueous and oil phases. As shown in Figure 1.1, amphiphilic molecules contain both hydrophilic and lipophilic structural fragments. The hydrophilic (water loving) portion of the molecule is polar, and thus has a strong tendency to dissolve in the aqueous phase due to polar-polar interactions or hydrogen bonding (H-bonding), whereas the lipophilic (oil loving) portion is usually a non-polar hydrocarbon, which readily dissolves in the oil phase. The strong interactions between water molecules arising from dispersion forces and H-bonding act cooperatively to squeeze the non-polar lipophilic portion out of the water, hence it is also referred to as hydrophobic. ”- chemical bonding I T T hydrophilic portion hydrophobic portion Figure 1.1. Structure of an amphiphilic molecule. Hydrophilicity and hydrophobicity have thermodynamic origins. There are two steps involved in dissolving solids in liquids: the break down of the solid state Structure and the reorganization of solvent molecules and solvation of the solute by the solvent. Figure 1.2 shows a schematic illustration. The free energy (AG) must be negative for the whole process to go forward. The process of breaking down the solid structure usually has positive enthalpy (AH) and positive entropy (AS). The solvation process, on the other hand, has negative enthalpy and negative entropy. The solubility is determined by the overall free energy change of the system. An example of a hydrophilic group is the hydroxide (OH) group. In liquid water a H-bonding network likely extends throughout the liquid. When OH comes in contact with water, it can act as a H-bonding donor or acceptor. Therefore the OH group is readily soluble in water since it can accommodate itself within the H-bonding network of water without seriously interrupting the network. Introducing a hydrophobic molecule such as a hydrocarbon into the water structure requires displacement of water molecules to accommodate the lipid molecule. This causes a loss in the total number of ways in which H-bonds can be built into the water structure, and correspondingly a decrease in the entropy of the system. The enthalpy change for solvation of lipids by water is small and negative due to the low polarity of the lipid molecule. The overall process favors a positive free energy change, preventing the lipid from dissolving in the aqueous solution.“ Introducing hydrophilic groups such as a carboxylate or a polyether into the hydrophobic lipid chains yields amphiphilic molecules. Because of their striking difference in the solubility preferences of their hydrophilic and hydrophobic segments, amphiphilic molecules have a strong tendency to aggregate at the interface between polar e 8.2538 5 8238 Lo sous—88% no... 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All of these useful properties are due to the amphiphilic structure of the surfactant. The hydrophilic group tends to dissolve into the aqueous phase while the hydrophobic group has only a Slight affinity for water. Water molecules have a strong affinity for one another which causes the hydrophobic groups to withdraw from the surrounding water. The eventual fate of the hydrocarbon group depends on the properties of the interface. The synthesis and applications of surfactants have been known since ancient times. Soap is the first synthetic surfactant. In the early days of soap manufacturing (Scheme 1.1), animal fat (triacylglycerols) was hydrolyzed with wood ash (K2C03), in a process called saponification. Wood ash was used as a source of alkali until the mid- 18005, when the Leblanc process for producing NazCO3 was invented, making NaOH commercially available. Soaps exert their cleansing action due to their amphiphilicity. When soaps are dispersed in water, the long hydrocarbon tails cluster together in a lipophilic ball, while the ionic head groups dissolve in the water. These spherical clusters are called micelles. Grease and oil droplets are solubilized in water when they are coated by the non-polar n CHz—O—C—R wood ash CH OH R (K2003) i? . + . 2 (:H—O—C—R : 3 RCOK 4. CHOH 0 water CHZOH “ soap C —O—C—Fl H2 glycerol a fat R = C15 - C19 lipid Chains. Scheme 1.1. Early method for manufacturing soap. hydrophilic head hydrophobic tail Figure 1.3. Dispersion of oil droplets into aqueous solutions of surfactant.2 tails of soap molecules (Figure 1.3). Once solubilized, the grease and dirt can be washed away. The aggregation of surfactants was unknown until 1920, when McBain and Salmon investigated the osmotic activity of a 1 mol/L solution of potassium stearate at 90 °C. They found that the concentration of the osmotically active material was 0.42 mol/L and hence concluded that considerable association had occurred in the solution. McBain suggested that the associated units should be called micelles. Surfactants find wide applications in biological systems and in the chemical industry as detergents, paints, cosmetics, pharmaceuticals, pesticides, fibers and plastics. Therefore a variety of surfactants have been designed to suit different applications. Most have similar hydrophobic groups, which are either long hydrocarbon chains (18 to 8 carbon atoms) or a short-branched alkylbenzene. As most of the surfactants have the similar hydrophobic groups, they are usually classified by their hydrophilic portion.” Table 1.1 lists common synthetic surfactants. There are three major classes of surfactants: ionic, zwitterionic and nonionic. Ionic surfactants have charged hydrophilic groups such as carboxylate or quaternary ammonium ions, which can be further divided into the anionic and cationic subclasses depending on whether the group carries a negative or positive charge. Zwitterionic surfactants have both positive and negative hydrophilic groups. Nonionic surfactants do not have a charge, the hydrophilic character is derived from neutral polar sites such as hydroxyl or ether groups.6 Nonionic surfactants with oligoethylene oxide segments are particularly important and their solution and solid-state properties have been well studied.7’8 The hydrophilicity .x..§£:ozlziaxfu§_ 8:8 E:mcoEEmARE—Euhocamonmvmmm .xfimmuxolrmm 38 83:88:58 .0“th -xfimmofmm £8 538:8 eta—cog. .XAQEUVLM 328 Esconmmofi EEBEO kwmeZm £8 222522.33in 88—38 2:280 .XEAAAIUVfLAM 8:8 EacoEEm hash: $39508 39:55 .xifiurzm 8:8 EacoEEm EEBEO +2..~m0mm £8 03558 +2..U~A~Om£0v~0mm 8:8 uEfiofiaaoC—zwch +E.~OZ-ZM 8:8 ongoEZ +2.-~O%.Mvm 8.8 822805 8m? 0E2 LZQROAOM 2.8 880885 32895 .2m.ann—M 8:8 camconmmonm .2488 ea... 0.3388528 +2..~Omm 8:8 2252232 88328 2:25.. +2..mOmEZm £8 03828—322 +2..nOmOM 88 28—8 .32 +2..AOmm 8:8 828—8832 +2.-~OUM Samoa 278 Aoaofie—Eofiaxofiao .32 53ELQ~E~§O use: 55% Eeugak beMquraau. Demand .838» R5583 28 “588.38 mo motowouau AA 035.“. 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The formation of micelles governs aggregation in solution and bulk, as well as the phase structures of the amphiphile.2 A characteristic of a surfactant is that its concentration is higher at the air-water interface than in the bulk liquid. This is a consequence of the amphiphilic structure of the molecule, because only the interface can satisfy the solubility requirements of both portions of the molecule. In the case of the air-water interface (Figure 1.5), the llllll'llll air or oil phase interface aqueous phase Figure 1.5. Aggregation of amphiphiles at interfaces. hydrophobic hydrocarbon chains are oriented away from the water. Absorption of a surfactant at the interface results in a decrease of H-bonding among surface molecules and a decrease in the surface tension. A plot of the surface tension against concentration (Figure 1.6) shows that the surface tension falls rapidly with an increase in the concentration of surfactant until a point is reached where the surface tension is nearly constant. This point corresponds to coverage of the surface by a monolayer of surfactant. Further increases in surfactant concentration cause the formation of spherical assemblies in the solution known as micelles where the interior of the micelle resembles a separate hydrocarbon phase. The concentration at which micelles first form is called the critical micelle concentration(CMC), and is usually less than 1% for most surfactants. A monolayer of surfactant / surface tension - o ou-umooo surfactant concentration Figure 1.6. Surface tension of surfactant solutions versus concentration.2 13 Spheres are the most common shape of micelles at concentrations just above the CMC. The micelle shape at higher concentrations is determined by the packing ratio P, which is defined by Equation 1.1 P = ac I ah Equation 1.1 where 3C is the cross section area of the alkyl chain and ah is the cross sectional area of the hydrophilic head group as defined in Figure 1.7 . If the groups are of relatively equal cross-section, i.e., P = 1, they will pack easily provided that the surface (”N“) 4—— area ac ~h-M Figure 1.7. Effective head and chain group areas in surfactants.2 is planar. If the groups are of very different cross-sections such that the hydrophilic group is larger than the hydrophobic group, i.e. P < 1, then packing causes the surface to curve towards the smaller group. For example, the carboxylate group has a larger cross- area than the hydrocarbon chains, so P < 1 for the soap molecule. At higher concentrations (IS-25%), the soap micelles adopt a rod-like structure to accommodate 14 the extra volume of the carboxylate group. For phospholipids, P = l and the stable structure is a bilayer.1 In Figure 1.8, the appearance of spherical, rod-like or lamellar shape micelle phases is due to the concentration and structural feature of the amphiphiles. Further increase in concentration results in the formation of a liquid crystal phase, and eventually, the bulk amphiphile. o—— ——o 03/0 8800— ——‘f, °/\\00 00° -———o .l, 00—— A) sphere B) rod C) lamella Figure 1.8. Structures of micelles in dilute solution (A) and concentrated solutions (B, C).1 2) Solid state structures of amphiphiles The crystalline phases of amphiphiles have the highest order and are the densest phases they form. The crystal structures are largely determined by the amphiphilicity of the molecules. Although there are numerous kinds of amphiphiles, they all have similar lamellar structures in the solid state. The polar hydrophilic heads aggregate to maximize the polar-polar interactions, while the non-polar lipid portion, which usually is a straight chain hydrocarbon chain, adopts a zig-zag conformation and crystallizes in adjacent layers. The exact structure within each lamella is determined by the individual 15 amphiphiles and their history of crystallization. Three different structures are possible for lamellae: bilayer crystal, interdigitated and monolayer structures as indicated in the schematic drawing in Figure 1.9. i) The bilayer crystal structure Bilayer packing is the most common solid state structure of amphiphilic materials. As shown in Figure 1.9 A, bilayer packing allows the separate aggregation of hydrophilic and hydrophobic groups and minimizes the contact of the two groups. Bilayer packing can be found in different kinds of amphiphilic materials, including ionic surfactants, lipid bilayers, and non-ionic surfactants. Figure 1.10 gives an example of the bilayer structure.”'” The first step in the assembly of bilayer structures from solution or melts is through polar-polar interactions of the hydrophilic groups, which is sometimes called head-to—head pairing. Many of these pairs are assembled within the x,y-plane to - form a bilayer. The bilayers then stack together in the z direction to form bulk crystals. The chains in the assembled bilayer can be perpendicular or tilted. Ordinarily during stacking, the atoms in the outer planes do not penetrate significantly into the opposing plane of the adjacent bilayers. The stacking of bilayers is a thermodynamically favored process. The surfaces of an isolated bilayer are interfaces, while a surface buried within a bulk phase is not. As a result, stacking decreases the ratio of interfacial area to volume and thereby decreases the specific surface area. ii) Interdigitated structure Interdigitated structures are very common among solid-state amphiphiles. They can be viewed as adjacent bilayers merging into one another. As in bilayer packing, the 16 Illllllllllll lilillllilllllli B C Figure 1.9. Layered structures of lamellar shaped amphiphiles. (dark) polar head groups; (light) lipid tails. A) bilayer packing; B) a. partially interdigitated structure. b. fully interdigitated structure. C) monolayer packing. Figure 1.10. Solid state head-to-tail bilayer structure of the monohydrate of l- lauroyl- l ,3-propanediol- l-phosphocholine. '2 interdigitated structure retains a layered structure, but it is usually more stable and has a higher density than the bilayer structure. As shown in Figure 1.9 B, there are two types of interdigitated structures, a where only the hydrophobic tails interdigitate, and b where both the hydrophilic chain and hydrophobic chains interdigitate's'” Amphiphiles that have relatively equal cross sections are more likely to be fully interdigitated as in b. Such an arrangement is not very common since amphiphiles usually form stable bilayers and therefore partial interdigitation as in a, is more common.‘8 The size of the hydrophilic group often determines whether interdigitated structures will from. In zwitterionic amphiphiles, the hydrophilic group is composed of Oppositely charged functional groups. These large head groups create void space that favors the interdigitation of the alkyl chains. Figure 1.11 shows examples of partially and fully interdigitated structures. 18 OH .3! (f a." Figure 1.11. Interdigitated packing structures. A) The fully interdigitated structure of N-dodecanoyl-N-methylglucamine. B) The partially interdigitated structure of methyl- 6-0-tetradecanoyl-B-d-glucopyranoside. Only the lipid tails are interdigitated. '5 iii) Monolayer structure Monolayer structures have head to tail packing in the z direction of the amphiphilic molecules as shown in Figure 1.9 (C). The packing is still layered but the polar face of one layer lies next to the non-polar face of the adjacent layer. These monolayer structures are often found in smectic liquid crystals,19 but they are relatively rare in solid state amphiphiles because the interface between the polar and non-polar phases destabilizes the crystal structure. However, if intramolecular H-bonding can stabilize the polar head group, the monolayer structure is favored.”21 In the molecular packing of the ldeoxy-(N-methylheptylamido)-D-glucitol amphiphile (Figure 1.12), H- 19 bonding in the head group stabilizes the crystal structure and favors an overall monolayer , ' i ‘ C . ...O 0... structure.22 Figure 1.12. Monolayer crystal structure of N-dodecanoyl-N-methylglucarnine.22 Tilting of the lipid tails and polar head groups can occur in all three packing structures. In fact, tilting of the lipid tails 25° to 30° relative to the surface normal is a common feature found in the solid state structure of amphiphiles. 1.2 Diblock Copolymer Phase Behavior Different polymers can be combined into a single material in many ways, which leads to a wide range of phase behaviors that directly influence the associated microstructure properties. The simplest case is a binary mixture of homopolymers. At equilibrium, such a mixture consists of either one or two phases. In the event of phase 20 separation, interfacial tension favors a reduction in the surface area which leads to macroscopic segregation. This is a direct consequence of the well-known relationship for the free energy change for mixing (AGmix) given by Equation 1.2. AGm = AHmix - TASmgx Equation 1.2 In case of a diblock copolymer system i.e., polystyrene—block-polyiSOprene (PS- PI, Figure 1.13), the heat of mixing (AHmix) can be calculated using the Flory-Huggins equation as shown in Equation 1.3 AHmix = kT x Npsz; Equation 1.3 where xis the Flory-Huggins parameter that reflects the interactions of the two blocks, N95 is the number of repeating units of segment PS, and VP] is the volume fraction of segment PI. Polymers have a very small entropy of mixing (ASmix) due to their high molecular weight. Therefore, a slightly positive enthalpy change (AHmix) due to endothermic mixing is sufficient to produce a positive free energy change (AGmix), thus resulting in incompatibility (i.e., polymer phase separation). In a binary mixture of homopolymers, the incompatibility of the blend components provides a driving force for each polymer to aggregate in separate phases. These two-phase systems are coarse dispersions in which the particles are usually large enough to make the blends opaque. The formation of diblock copolymers is a method for mixing chemically different polymers. Covalently bonding two polymers together has a dramatic influence on the microstructure of the materials. The most significant factor in determining block copolymer phase behavior is the covalent bond that restricts the macroscopic separation of chemically dissimilar polymer blocks. This constraint leads to the formation of 21 microscopic heterogeneities in composition at length scales comparable to the molecular dimensions, that is, around 5 to 100 run. As shown in Figure 1.13 A the PS and PI segments still segregate, but the domains have dimensions corresponding to the size of the single blocks. In addition, the domains have a uniform size, and can form ordered mesophase lattices. The micro-domain structure changes with changes in the volume fraction of the blocks.23 At equilibrium, an ordered block copolymer will be macroscopically oriented, analogous to a single crystal of low molecular weight materials. The relationship of morphology to the relative composition of the PS block in a PS-PI diblock system is shown in Figure 1.13 B. 1.3 Nanometer-Scale Ordered Materials Nanometer-scale materials are defined as having structural features or characteristic lengths between 1 and 100 nm. Nanomaterials usually exhibit peculiar and interesting characteristics including quantized excitation, single-electron tunneling, and metal-insulator transition.”27 These phenomena occur in structures small enough that quantum mechanical effects dominate the bulk properties of materials. Fabrication of nanometer-scaled ordered materials poses great and exiting challenges to chemists, physicists and materials scientists. The fundamental study of phenomena that occur in structures having dimensions in the 1-100 nm regime has already evolved into a new field of interdisciplinary research that is sometimes referred to as nanoscience. The conventional way to fabricate nanometer-scale materials is to use lithography or scanning probe microscopy.28'29 Photolithographic methods all share the same operational principle: exposure of an appropriate material to electromagnetic radiation introduces a latent image (usually a difference in solubility) into the material as 22 w W fl Liv p3 PS PS PS, PI PI PI PI Spheres Cylinders OBDD Lamellae OBDD Cylinders Spheres 1 2 3 4 5 6 7 l i l l l 5 fs 0.17 0.28 0.34 0.62 0.66 0.77 A 60 i : i i : so — a s s s I .2 35 4 55 5 65 7 4o .. : E 5 5 N95-” ordered phase; g i 30 - a a : s zo .. E s s i 10 _ disordered phase 0 I l l I f, 0.0 0.2 0.4 0.6 0.8 1.0 B Figure 1.13. Phase behavior of diblock polystyrene-block-polyisoprene (PS-PI). A) Microstructural changes of PS-PI as a function of the PI block volume fraction (fs). spherical structures (1, 7) have a body centered cubic structure. Cylindrical shapes (2, 6) have hexagonal packing. Bicontinuous double diamond phase (OBBD) (3. 5) exists over a narrow compositional range (0.288-0.34, 0.66-0.73). B) Phase diagram for the PS-Pl copolymer. Nps.” is the degree of polymerization of the PS-PI. Ordered phases correspond to the numbers used in A.23 23 a result of a set of chemical changes in its molecular structure. The latent image is subsequently developed into a relief structure through the process of etching. Methods based on writing with particles (electrons or ions) usually accomplish the same task but use a scanned beam or projected image of energetic particles rather than photons. Exposure is usually achieved either by interposing a mask between the source of radiation and the material or by scanning a focused spot of the source across the surface of the materials. The advantage of lithography is that it is fast and it can easily be used to make replicas. Decreasing the wavelength of light enables the formation of very small- scale patterns. Electron beam lithography can be used to define features < 0.1 nm.30'31 In recent years, there has been a radically different approach to the fabrication of nanostructures, the self-assembly of macromolecules. The concept of self-assembly originates from the exploitation of intermolecular forces. Self-assembly occurs in biological processes such as the folding of polypeptide chains into functional proteins and the formation of cell membranes from phospholipids. In self-assembly, subunits spontaneously organize and aggregate into stable, well-defined structures based on non- covalent interactions. The information that guides the assembly is coded in the characteristics (for example, topographies, shapes, surface functionalities and electrical potentials) of the subunits, and the final structure is reached by equilibrating to the form of the lowest free energy. Because the final self-assembly processes occur close to or at thermodynamic equilibrium, they tend to reject defects.”34 A variety of strategies for self-assembly have been deve10ped for fabricating nanometer-scaled ordered structures. Among them, three major approaches have been proven successful: the use of phase-separation in block copolymers to give ordered solid 24 state structures,23 the aggregation of surfactant or colloidal particles to give uniform size and shape particles,35 and the use of liquid crystals to define temporarily ordered phases 6 that can be cross-linked to form dimensionally stable ordered structures.3 1 Diblock copolymer phase separation Diblock copolymers form domains that have a uniform size and assemble into ordered mesophase lattices. The size of micro-domains, which vary from 5-100 am, can be controlled by changes in the volume fraction of the blocks.23 These features have been used to fabricate nano-ordered materials. Several successful systems have been developed using diblock copolymers. Ward37 used a composite diblock copolymer system to control dipole alignment at the nanometer scale as illustrated in Figure 1.14. Addition of 2—chloro-4-nitroaniline (CNA) to diblock copolymers of PEO and PS, poly(ethylethylene), or poly(ethylenepropylene) results in selective partitioning of CN A into the polar PEO domains. The CNA is confined within the PEO domains due to its immiscibility in the PS block. It may be feasible to orient the domains and/or the chromophores by use of an external electric field. Consequently, these materials can be described as rigid crystalline molecular complexes embedded in a robust, ordered polymer microstructure. This control of hierarchical order occurs over several orders of magnitude of length. This suggests a route to permanent macroscopic ordering of functional molecules, which is a desirable feature for applications such as optoelectronics. The conformational rigidity associated with these systems offers considerable advantages for the design of SHG materials as entropically driven disordering is inhibited compared to noncrystalline polymer-chromophore materials. 25 m OM07” I H2N O N02 Cl Polystyrene-block-polyethylene oxide (PS-PEO) 2-Choloro-4-nitroaniline (CN A) PEO & CNA complex {Ill/f/IIJ/r'l/l/ -‘ Ar its”. "figur‘iél‘. ." 3“: J’b'w. .'. 1 '3 ti ‘4‘.“ I.” ll/I/I/J/f/J {5‘ xtrsts‘tyymw 3m", {‘4' “A we :t‘f! I/ .. [A &WM&¢MflJE¢ ' PS lamellar packing of the block hexagonal packing of the block copolymer copolymer ' ff/f/JJIIJ/‘f/lf/I 1131, aamzmmmm a, ,4 wall/ww/w/w/nwfiv f, '2’ ,. f. ”hip-7‘ _.",“V!"-."»‘:- '7 . ,‘ . amt-waxemxm-d.) 3.. .r Figure 1.14. 2-Chloro-4-nitroaniline and its polystyrene-block-polyethylene oxide complex.” 2 Amphiphiles and colloidal assemblies In solution, surfactant molecules self assemble to form aggregates. At low concentration the aggregates are generally globular micelles. With increasing surfactant concentration, micelles grow, elongate, and evolve from more or less flexible rod-like micelles to cylindrical or lamellar shapes. Similar effects are seen upon the addition of salt or alcohol. The structure and size of the micelle can be controlled by the nature of the hydrophilic head group, the size of the lipid portion of the amphiphile and the solvent.38 Amphiphilic molecules spontaneously self-assemble to form highly flexible locally aggregated structures with average sizes from 10 nm to several microns. These self- assembling effects can be used to fabricate perfect nanometer scale crystallites that can be identically replicated in unlimited quantities. For example, Motte39 and coworkers achieved control over the size of silver sulfide semiconductor particles in functionalized reverse micelles by changing the water content. The size of the crystallites ranged from 2 to 10 nm and varied linearly with water content. 3 Liquid crystal assemblies Liquid crystals (LCs) are molecules that self-assemble into organized phases that are intermediate between crystalline solids and isotropic liquids. In these mesophases, the molecules are dynamic and behave like a viscous fluid, but they still maintain a degree of order reminiscent of a crystalline solid. LCs may adopt various phases depending on the temperature and concentration of solvent. Through the appropriate design of LC monomers and in situ polymerization techniques, robust networks can be achieved that preserve the nanostructure. The combination of these techniques affords ordered polymer-based materials with a degree of sophistication unparalleled in the fabrication of 27 synthetic polymers. These organic assemblies are then used for the construction of a variety of advanced functional materials.”42 Gin has used this approach to prepare ordered nanostructured optical materials.36 Polymerizable 1yotropic liquid crystals (LLCs) were used to synthesize hexagonally ordered poly(p-phenylene vinylene) (PPV) nanocomposites as shown in Figure 1.15. LLC monomers were used to form an inverted hexagonal phase in the presence of an aqueous PPV precursor solution. Subsequent photopolymerization to lock in the matrix architecture, followed by thermal conversion of the precursor to PPV in the channels, yields the final nanocomposite. The photoluminescence of these materials is very different from that of pure PPV. The nanometer-scale dimensions of the composites can be tuned by modifying the ionic head group and the organic tails of the LC monomer. The three different approaches described for fabrication of nanometer-scale ordered materials are related, as there is no clear-cut boundary between surfactant aggregation and the formation of liquid crystals. Most liquid crystal molecules used for self-assembly are indeed amphiphiles and many surfactants can form ordered liquid crystalline structures at high concentration. Some researchers have used a combination of these methods to obtain better results. J enekhe synthesized block copolymers that aggregate like surfactants to make self-ordering hexagonal structures.43 As shown in Figure 1.16, rod-coil diblock c0polymers, dispersed in a good solvent for the coil-like polymer, self-organize into hollow spherical micelles having diameters of a few microns. Long-range, close-packed self-ordering of the micelles produce highly iridescent periodic . . 4 microporous materials. 3 28 O(CH2)11OCCH=CH2 Na" OOC“O(CH2)1OIO1OCCH=CH2 O(CH2)11OCCH=CH2 Amphiphile with polymerizable double bonds Amphiphile self-assembled into hexagonal liquid crystal structure Cross-linked PPV amphiphiles nano-crystal V - n SM82 - n HCI Poly(p-phenylenevinylene) (PPV) Figure 1.15. Synthesis of PPV nanocomposites with hexagonal symmetry using polymerizable 1yotropic liquid crystals. 29 n m 0:1 O E—c—éCH—CHfi— O Poly(phenquuinoline)—block-polystyrene rod—block-coil #2563 rod coil good solvent for coil Rod part aggregates in the middle of the micelle. .36.. "‘ I 2 11m diameter ‘i g g*w§:%§f§$?% v . ‘8 a Figure 1.16. Molecular structure of a rod-coil diblock copolymer and schematic illustration of its hierarchical self-assembly into ordered microporous materials.43 30 1.4 (1) (2) (3) (4) (5) (6) (7) (8) ' (9) (10) (11) (12) (13) (14) (15) (16) (17) References Tadros, T. 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Cryst. 1985, 131, 245-255. Jeffrey, G. A. Mol. Cryst. Liq. Cryst. 1990, 185, 209-213. Bates, F. S. Science 1991, 251, 898-905. Likharev, K. K. IBM J. Rex. Dev. 1988, 32, 144-158. Likharev, K. K.; Claeson, T. Sci. Am. 1992, 80-85. Reed, M. A. Sci. Am. 1993, 118-123. Vijayakrishnan, V.; Chainani, A.; Sarma, D. D.; Rao, C. N. R. J. Phys. Chem. 1992, 96, 8679-8682f. Moreau, W. M. Semiconductor Lithography: Principles and Materials New York, 1988. Brambley, D.; Martin, B.; Prewett, P. D. Adv. Mater. Opt. Electron 1994, 4, 55- 75. Muller, D. A.; Tzou, Y.; Raj, R.; Silcox, J. Nature 1993, 366, 725-727. Batson, P. E. Nature 1993, 366, 727-728. Ringsdorf, H.; Schlarb, B.; Venzmer, J. Angew. Chem. -Int. Edit. Eng]. 1988, 27, 113-158. Whitesides, G. M.; Mathias, J. P.; Seto, C. T. Science 1991, 254, 1312-1319. Whitesides, G. M. Sci. Am. 1995, 273, 146-149. Pileni, M. P. Langmuir 1997, 13, 3266-3276. Gin, D.; Smith, R.; Deng, H.; Leising, G. Synth. 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Science 1999, 283, 372-375. 33 CHAPTER 2 Thermal and Structural Properties of Amphiphilic Diblock Oligomers 2.1 Introduction Materials structured at the nanometer scale have attracted increasing research interest in the past decade due to their unique mechanical, electronic and optical properties."4 One route to nanomaterials is through molecular assembly processes such as the phase separation of block copolymerss‘6 and surfactant or colloidal self-assembly.7"° Such processes lead to diverse materials ranging from nanoporous silicas to photonic band gap structures. Similar results are obtained with amphiphilic biomaterials such as phospholipids which self-assemble to form hexagonal liquid crystalline structuresll in solution or bilayer structures]2 in the solid state. Examples of the use of the ordered structure of amphiphilic materials to fabricate nanometer scale materials (Figures 1.15 and 1.16) were discussed in CHAPTER 1.1 "'3 Modifying materials to make them amphiphilic is an effective strategy for inducing self- organization in materials. For example, DNA-amphiphilic complexes (Figure 2.1), prepared by replacing sodium counter cations by cationic amphiphilic lipids, crystallize into oriented fibers due to the phase structure induced by the amphiphiles.l4 A water- insoluble DNA-amphiphile film was prepared by casting from organic solvent, and stretching produced oriented DNA strands with their axes aligned along the stretching direction. Recently, peptide segments were spliced into the side chains of ionic amphiphiles in molecules that possess a hydrophilic ammonium group, a tripeptide group, and one or two hydrophobic alkyl chains.” The peptide-modified amphiphilic molecules 34 CH3 1 CH3(CH2)g—(OCHZCH2)4—l}E-CH3 %—I=I>=o CH3 cl) c amphiphilic molecule DNA segment A a; o O .5? ' a 3 ’ . aligned amphiphiles :3. . O (D E. 'r' 2:. s .e- A - =3- DNA double helix B Figure 2.1. Surfactant DNA complexes. A) Molecular structure of amphiphiles bonded to the DNA segment. B) Fiber structure of aligned amphiphiles attached to the DNA double helix.” 35 orientated perpendicular to the bilayer plane, interpeptide H-bonding easily formed between neighboring molecules. By controlling the crystallization conditions, the amphiphilic side chains aligned the tripeptide core into three different types of membrane structures as shown in Figure 2.2: a bilayer structure, a reversed bilayer structure or an interdigitated monolayer structure. Besides amphiphiles, block copolymers are another choice for the preparation of nanometer-scaled ordered materials because their phase structure and morphology can easily be controlled by the volumes of the blocks.‘5 C0polymers can self-assemble into a variety of solid state nano-scale structures ranging from ordered spheres, or cylinders to reverse phase structures. Non-ionic amphiphilic materials with long hydrophobic and hydrophilic side-chains possess the properties of both the amphiphiles and block copolymers. One class of nonionic amphiphiles uses oligo(ethylene oxide) as a hydrophilic head group and an oligoethylene segment as a hydrophobic group. This class of materials has interesting solid-state structural properties due to the different characteristic conformations of the two blocks.'6"8 Linear alkyl segments typically crystallize in a planar zig-zag conformation, and when polyethylene (PE) chains exceed 150 carbon atoms, they fold to give lamellar crystals. Because chain folding of PE is kinetically controlled, lamellae with different thickness can be obtained. Besides chain folding, there are four crystalline polymorphs of PE that can be obtained under different crystallization conditions. An orthorhombic unit cell with chains parallel to the c axis is the most stable polymorph. A less stable orthorhombic form and two monoclinic structures were also observed.'9'2| DSC heating scans of crystalline PE show multiple 36 iiliilfitt 11211111111 lliiiilii bilayer structure :20 H awhiphile peptide 1 J v v X Y 1 A) bilayer structure 8) interdigitated C) reversed bilayer monolayer structure stucture \e '1' 0 R2 '1 ° /N 4, the conformation of ethylene oxide is length dependent. When y < 3 both the alkyl and ethylene oxide chains are planar zig—zag as the closely packed alkyl chains force the short ethylene oxide chains into a planar zig-zag structure.34 When y > 4, the ethylene oxide segments adopt a 72 helical structure.” Usually the axis of the alkyl chain is bent 25° to 30° relative to 39 the helical ethylene oxide chain (Figure 2.3 A).36'37 When y = 3, 4, the conformation of C,,EOy usually depends on the thermal history of the material.38 The hydroxide group is reported to induce both a helical structure in the ethylene oxide units and a bilayer-packing pattern in the material (Figure 2.3 B)”33 A related group of surfactants are the triblock oligomers CxEOyCx as shown in Scheme 2.1. In these materials, the ethylene oxide portion crystallizes in a planar zig-zag form when y < 7 and x > 5. The planar zig-zag conformation of the alkyl chain sets the crystal structure, and the shorter ethylene oxide segment follows the trend and also crystallizes in the zig-zag format. The helical form is seen when y = 7 as shown in Figure 2.4, since a full unit cell of the ethylene oxide chain allows parallel packing of the alkyl segments.39 Increasing y leads to increasingly stable helical structures. The phase separation of a diblock oligomer or polymer defines an interface at the junction of the two chains. Small groups inserted between the two chains will have two effects depending on the size of the inserted groups. Large asymmetric molecules will disturb the crystal structure of the amphiphilic material, while a smaller, more symmetric molecule could be accommodated in the crystal, and potentially be aligned by phase separation and crystallization of the diblock oligomer. In this research we placed a benzene ring at the interface, because it is large in two-dimensions and offers the potential for 1H: stacking effects40 in the third dimension that would facilitate self-assembly. Another attractive property is that the benzene ring can be chemically modified to add other functional groups. The phase separation and crystallization of the blocks attached to the ring should lead to an ordered array of the benzene ring. Thus this approach opens 40 B Figure 2.3. The structure of C,,EO,. A) Molecular conformation of C,EO,: seven ethylene oxide units form a 72 helix and the axis of the planar zigzag alkyl chain is offset 30° from the axis of the ethylene oxide helix. B) The bilayer crystal structure Of CgEOy-32' 33. 36, 37 41 Figure 2.4. C,EO,C,, a molecule with a helical ethylene oxide core.39 a new synthetic route to ordered solid state materials. Understanding the crystal structure and thermal behavior of these groups of compounds is important for defining the design rules for these materials. 2.2 Results 1 Materials Synthesis 1) Acronyms for compounds All compounds described in this chapter contain three segments: a methylated oligo(ethylene oxide) chain, an n-alkyl chain and a 1,4-substituted benzene core that connects the two chains. For simplicity, a nomenclature system similar to that commonly used for PEO/PE surfactants is used to referring to these compounds. The ethylene oxide repeating unit is abbreviated as E0, the methyl group and methylene unit as C, and Ph for the benzene ring that joins the chains. Subscripts are used to indicate the number of EO and C repeating units. The CIEOy and C, chains are attached to the benzene ring in a 1,4 relationship, which is not explicitly defined in the acronym. An example of the naming protocol is shown in Scheme 2.2. 42 Scheme 2.2. Example of the acronyms used for naming compounds CH3(C H2)x.1—.~O(C HZCHZO)yC H3 cxpheoyc, 2) Synthesis of exact length oligo(ethylene oxide) monomethyl ethers Having significant amounts of exact length of ethylene oxide monomethyl ethers (4, Scheme 2.3) is important for studies of the solid state properties of these compounds, but only compounds with five or less ethylene oxide repeating units are commercially available. To prepare longer compounds, we adapted the method developed by Chen and Baker"I to the synthesis of 4 (y = 4 to 7) (Scheme 2.3). Commercially available diethylene glycol, triethylene glycol and tetraethylene glycol were monotosylated by reacting the die] with 20% of the stoichiometric amount of tosylchloride and KOH in THF. The monotosylated glycols were protected with THP, and the sodium salts of commercially available 4 (y = l to 3) were used to displace the tosyl group and afford 3. Removal of the THP group gave the exact length oligo(ethylene oxide) monomethyl ether, which was purified by vacuum distillation. Table 2.1 shows the combinations of starting materials used to synthesize the products. All steps in the synthesis have > 90% yields, but the distillation of the longer chain 4 molecules requires high temperatures, and partial thermal degradation of the product limits yields to near 40% as shown in Table 2.2. 43 Scheme 2.3. Synthesis of exact length ethylene glycol monomethylethers. KOH TsCl THF H(OCH20H2)aOH = Ts(OCH2CH2)aOH 1 O dioxane T OH 0 1 s TS(OC1"'1201"12)3C7IOj 2 CH3(OCH2CH2)bOH NaH,THF i H30+ ethanol CH3(OCH20H2)pH <—— CH3(OCHZCH2)a+b O 4 3 C1EOy y=a+b L ""v."-W Table 2.1. Combinations of ethylene glycol and monomethylated ethylene glycol used in synthesis of ClEOy (y = a + b)_ a 2 3 4 C1E04 CIEOS 3 C1506 C1507 Table 2.2. Overall yields and boiling points of CIEOy at 40 mtorr. y 4 5 6 7 bp (°C) 100 102 135 205 Overall yield (%) 42 56 41 35 3) C,PhEO,C1 High purity l-bromo-n-alkanes are commercially available with up to 20 methylene units. Conversion of the l-bromoalkane to a Grignard reagent followed by [1,3- bis(diphenylphosphino)-propane]dichloronickel(II) ((dppp)Cl2Ni) catalyzed coupling reaction with 4-chloroanisole gave the corresponding 4-alkylanisole. Because the methoxy group on the benzene ring retards the coupling reaction, the higher boiling THF was used instead of ether as the solvent. The coupling reaction took several days to reach completion, and more catalyst was occasionally added during the course of the reaction. After the phenol was deprotected with BBr3, oligo(ethylene glycol) tosylates (5, Scheme 2.4) were reacted with the deprotonated alkylphenol in THF to give the C,PhEO,C1 product. The final products were purified by flash chromatography followed by 45 Scheme 2.4. Synthesis of C,PhEO,C1. C H3 CH3(CH2)X.1MQBI' .CH3 (dppp)C|2Ni. THF 0 *0 Cl (CHzlx-ICHa 1) 3313 / 0142012 2) 1430* 0H 0(CH2CH2O)yCH3 N H r— 0 T3,: (creators O ‘ 7 (CHzlx-ICHS a ‘— CH3(OCH20H2)st ll 5 KOH CxPhEcht TsCl THF CH3(OCH20H2),DH 46 Table 2.3. Composition of the ethyl acetate/hexane elution system used for purification of CxPhEoyC; by column chromatography. x 1 2 3 4 5 6 7 14 35/65 40/60 50/50 60/40 80/20 80/20 80/20 16 35/65 40/60 50/50 60/40 70/30 80/20 " 18 35/65 40/60 50/50 60/40 70/30 80/20 90/ 10 20 35/65 40/60 50/50 60/40 70/30 80/20 90/ 10 * Purified by recrystallizition in pentane and ether. not synthesized recrystallization from ether. By using different starting reagents, a library of CxPhEoyCl compounds with exact length side chains were synthesized following Scheme 2.4. Table 2.3 shows the final compounds and the conditions used for their purification. 2 Properties of C,PhEO,C1 1) Thermal behavior The thermal properties of the CxPhEoyCl compounds were characterized by Differential Scanning Calorimetry (DSC). DSC runs for most samples were conducted in the same way. Five to ten milligrams of sample were heated to 100 °C. After holding at 100 °C for five minutes to erase any previous thermal history, the sample was quenched to —100 °C at 200 °C/min and held at that temperature for five minutes. The sample was then heated at 10 °C/min to 100 °C, held at that temperature for 1 minute, cooled at 10 °C/min to —100 °C, held for 1 minute, and finally heated at 10 °C/min to 100 °C. Since the C,PhEO,C1 compounds are small molecules, and have high diffusion rates, quenching 47 and slow cooling to the same temperature usually yields the same solid state structure.42 Thus, the DSC heating scans for quenched and slow cooled samples are nearly identical. The heating scans shown in the figures are for quenched samples unless otherwise noted. Shown in Figures 2.5 — 2.8 are the DSC second heating scans for the CxPhEoyCr series. Figures 2.9 - 2.12 show the corresponding cooling scans. Each figure contains DSC scans of compounds with the same alkyl chain length, and each scan is normalized with respect to the sample weight. The temperature range shown in the figures is limited to the region where thermal transitions were observed. As shown in Figure 2.13, there are six major types of thermal transitions for this group of pure compounds. Four are associated with heating endotherms, and another two are seen in cooling exotherms. A type I transition is a single melting endotherm and is usually observed in the melting of C,PhEO,C1 compounds with short ClEOy chains (y = 0, 1, 2). Type II transitions show pre-melting transitions followed by a major melting endotherm, and are commonly seen in CxPhEoyCl compounds with moderate length alkanes (x = 14, 16, 18) and long CIEOy chains (y = 5, 6, 7). There is evidence that structural reorganization is associated with the pre-melting transitions. Type III transitions, typically seen in the melting of CzoPhEoyCl compounds, show a pre-melting transition followed by two separate melting peaks. The experimental data point to these two transitions as the sequential melting of two different parts of the amphiphile. The fourth type of transition shows pre-melting followed by a melting endotherm, a crystallization exotherrn, and finally another melting endotherm. There is evidence that the two melting peaks correspond to the melting of two different crystalline phases. Type IV melting was seen for CxPhEoyCl when x = 14, 16 and 18. 48 C14PhEO7C1 C14PhE05C1 VM_ 2.5/L. M/li fl «ML— 11 C14PhEO4C1 V heat flow, endo ——> C14PhE0301 C14PhEO2C, I l l l I -60 -4O -20 0 20 40 60 temperature (°C) Figure 2.5. DSC heating scans of ClgPhEoyCl. Samples were melted to and held at 100 °C for 5 minutes and then quenched to -100 °C and held for 5 minutes before beginning the heating scans. 49 C16PhEOSC1 A C16PhEOSC1 W C15PhEO4C1 o C15PhE03C1 ‘O C m 3" .2 _ g C16PhEO2C1 .C C16PhEO1C1 L C16PhEOoC1 L -40 -20 0 20 40 60 temperature (°C) Figure 2.6. DSC heating scans of CuPhEOyCl. Samples were melted to and held at 100 °C for 5 minutes and then quenched to -100 °C and held for 5 minutes before beginning the heating scans. 50 80 C13PhEOyC1 T C18PhE05C, M C18PhEOGC1 «r I W 8 C18PhEO4C1\/_’_M c A 0) 3’ .2 r. E C18PhEOi _,/\..( L C18PhEO2C1 1‘ C13PhEO1C1 ’ ‘ F C18PhEOoC1 A h -40 -20 0 20 40 60 80 temperature(°C) 11 Figure 2.7. DSC heating scans of c,,PhEo,c,. Samples were melted to and held at 100 °C for 5 minutes and then quenched to -100 °C and held for 5 minutes before beginning the heating scans. 51 C20PhE0701 CzoPhEOSC, M I CzoPhEOSC1 CzoPhEO4C1 4L L r13: O ‘O C 0 a Q) .C CgoPhEOZC1 4A CzoPhEO1C1 1 C20PhEOoC, L -35 -15 5 25 45 65 as temperature (°C) Figure 2.8. DSC heating scans of CmPhEoyCl. Samples were melted to and held at 100 °C for 5 minutes and then quenched to -100 °C and held for 5 minutes before beginning the heating scans. C14PhEO-,C1 C14PhEOsC1 C14PhEOSC1 C14PhEO4C1 C14PhEO3C1 C14PhEOzC1 heat flow, endo —’ C14PhEO1C1 V i W ’ W i I I I I I -60 -40 -20 O 20 40 temperature (°C) Figure 2.9. DSC cooling scans of C,.,PhEo,c,. Samples were equilibrated at 100 °C for 5 minutes before beginning the cooling scans. C16PhEOSC1 C16PhEOsC1 ‘— C16PhEO4C1 0,,Pheoac, \r CW 11 ll C16PhEO2C1 W C16PhEO1C1 heat flow, endo w 7 C16PhEOOC1 1 5 40 65 temperature (°C) Figure 2.10. DSC cooling scans of CmPhEOYCl. Samples were equilibrated at 100 °C for 5 minutes before beginning the cooling scans. 54 C13PhE07C1 W C13PhEOaC1 W empheosc, iv C18PhEO4C1 C18PhE0301 C18PhE02C1 heat flow, endo ——> C13PhEO1C1 l V T l V 11 C18PhEOoC1 V I I I ~40 -20 0 20 temperature (°C) 40 60 80 Figure 2.11. DSC cooling scans of c,,PhEo,c,. Samples were equilibrated at 100 °C for 5 minutes before beginning the cooling scans. 55 C20PhEOyC1 WV C20PhEOsC1 N VV C20PhEO5C1 v W C20PhEO4C1 Czoph E0301 WI f ——> C20PhEO2C1 CzoPhEO1C1 U C20PhEOoC1 U heat flow, endo -40 -20 O 20 40 60 80 temperature (°C) Figure 2.12. DSC cooling scans of C20PhEOyCl. Samples were equilibrated at 100 °C for 5 minutes before beginning the cooling scans. 56 Melting endotherm: 1. Single melting endotherm. II. Premelting transitions and melting endotherm. III. Premelting transitions and double melting endothenns. IV. Premelting transitions, melting followed by crystallization and melting. 143.1} Increasing temperature Crystallization exotherm: V. Single crystallization exotherm. WT VI. Major crystallization exotherm and post melting transitions. 4 Decreasing temperature Figure 2.13. Major types of thermal transitions seen in DSC scans. 57 Only two characteristic crystallization behaviors were observed. A type V transition has a single crystallization exotherm and is seen in cooling scans of CxPhEoyCl with short CIEOy chains (y = 0, l, 2). A type VI transition exhibits a major crystallization exotherm and post crystallization transitions. There is evidence for structural reorganization during the post crystallization transitions. Type VI behavior is usually observed in cooling scans of the x = 18, 20 series of C2PhEOyC1 compounds. The melting points (Tm) and heats of fusion (AHfus) for CxPhEoyCl were obtained from DSC measurements. As shown in Figure 2.14, the Tm was taken as the onset of the melting endotherm, which was defined as the intersection of the linear portion of the low temperature side of the peak and the baseline. The heat of fusion corresponds to the area under the endotherm and was calibrated relative to indium standards. This method is consistent with the calibration protocol for the DSC equipment. Tables 2.4 and 2.5 show melting point and heat of fusion data for the x = 18, 20 series of CxPhEOyCl. heat of fusion /\ melting point Figure 2.14. Melting point and heat of fusion as measured by DSC. 58 Table 2.4. Melting points and heats of fusion of CmPhEOy from DSC measurements, 1St melting peak 2"" melting peak Crystallization peak y mp AH mp AH Crystallization point AH (°C) (J/g) (°C) (J/g) (°C) (HS) 0 51.5 176.3 46.6 180.2 I 46.2 144.0 43.6 148.2 2 37.4 133.1 35.0 132.6 3 30.0 75.5 35.9 69.3 35.2 72.0 4 31.2 74.9 36.1 62.9 35.3 66.7 5 35.6 138 35.2 62.6 6 36.9 143.2 34.4 55.4 7 38.3 139.0 33.6 52.8 59 Table 2.5. Melting points and heats of fusion of CzoPhEOy from DSC measurements, 1" melting peak 2'“l melting peak Crystallization peak y mp -AH mp -AH Crystallization point AH (°C) ("3) (°C) (J/g) (°C) (Va) 0 58.1 180.3 52.3 179.6 1 53.1 147.6 49.8 152.5 2 44.5 137.7 44.4 82.5 3 35.8 50.3 45.9 73.7 45.0 75.5 4 32.0 48.8 45.4 69.3 44.6 72.9 5 39.3 87.7 45.0 67.6 44.6 69.2 6 40.4 87.2 44.3 60.8 44.8 66.5 7 41.4 91.7 43.6 62.0 43.5 62.0 Some of the compounds with longer CIEOy chains show annealing effects. Figures 2.15 and 2.16 show DSC heating scans for compounds before and after annealing. Holding samples at temperatures 2 to 3 °C below the highest melting transition allows the structure to reorganize and assume a more stable structure. Annealing leads to three major types of changes in DSC scans as shown in Figure 2.17. For compounds that show type I behavior, annealing completely eliminates the pre-melting transition and increases the melting points and heat of fusion. Annealing of materials that show type II behavior eliminates the pre-melting transition and causes the two major melting transitions to merge, with corresponding increases in the melting points and heat of fusion. For compounds that show type III behavior, the annealing 60 C18PhEO7C, quenched C18Ph507C1 annealed C13PhE06C1 quenched C18PhE06C1 annealed l 1 heat flow, endo ——> C18PhE0501 quenched CwPhEOsC, annealed I I I -30 -1 0 1 O 30 50 temperature (°C) Figure 2.15. Comparison of annealed and quenched DSC heating scans of CmPhEOyCL 61 CzoPhEO7C1 Quenched WM CzoPhEO-,C1 annealed CzoPhEOSC, quenched M C20PhE0501 annealed CzoPhEO4C, quenched Ad CgoPhEO4C1 annealed l 1 H heat flow, endo —> CzophE03C1 QUGUCL’J A CzoPhEOSC1 annealed CzoPhEO2C1 annealed JL CzoPhEO2C1 quenched l 1 -45 -25 -5 15 ' 35 55 temperature (°C) Figure 2.16. Comparison of annealed and quenched DSC heating scans of Wop. 62 I. Annealing of a single melting endotherm with premelting transition leads to a higher melting endotherm. Quenched Annealed II. Annealing of double melting endotherrns with premelting transitions leads to a single higher melting endotherm. Quenched Annealed III. Annealing of double melting endotherrns with premelting transitions leads to a double melting endotherm. Quenched Q Li? L? Annealed Figure 2.17. Major types of DSC thermal transitions seen in annealed samples. 63 effects are not as systematic, but they all lead to an increase in the melting point and heat of fusion. 2) Low angle powder X-ray diffraction Most of the C,PhEO,C1 compounds (except C14PhE03C1 and C14PhEO4C1, which are liquids at room temperature) were characterized by low angle (05° to 15°) powder X-ray diffraction (XRD). Low angle XRD can provide information about the nanometer scale structure of materials by analysis of the d-spacings. For example, a well- defined series of 001 lines is consistent with a layered structure and the layer spacing may be calculated using the Bragg equation. (Equation 2.1) d = l. / bin 0 Equation 2.1 Figures 2.18 - 2.21 show XRD data for CxPhEoyCl. Each figure shows scans for compounds with the same alkyl chain length normalized relative to the highest intensity reflection in each scan. The most prominent features in these data are the 001 reflections. The d-spacing calculated for each compound (Table 2.6) was derived from an average of the 00! reflections. Reflections due to the lamellar packing of the compounds become more prominent as the side-chain lengthens. In the C14PhEO,C1 series (Figure 2.18), y = 5, 6 and 7 show diffraction data characteristic of lamellar packing, while the data for y = 0, and 2 may represent a more complicated structure or polyrnorphorism. Simply increasing the alkyl chain enhances the lamellar structure of these materials. Thus the x = 16, 17 and 18 members of the CxPhEOoCl series of compounds all show scattering data characteristic of perfect lamellae. The CzoPhEoyC; series of compounds shows systematic increase of the d- spacings as y is increased (Figure 2.21). The ClsPhEoyCl series follows the same trend, X10 1‘ 014131150701 A __._A X10 C14PhEOsC1 1 C14PhE05C1 l l 4? _.. 2 A .9 .E C14PhEO2C1 A 71 c,,pheo,c, A L e. A A 0,,Pheooc, 0 2 4 6 8 10 12 14 20 16 Figure 2.18. Low angle XRD data for c,,PhEo,c,. The samples were cooled from the melt and held at room temperature for ten to twenty hours before analysis. L C16PhE06C1 J1 C16PhE05C1 A A c,,,r>hrso.,c1 __ g r: C PhEO C :2 A A A A 16 3 1 C16PhE0201 L J1 A x A A A J C16PhEO1C, JL 4 A A C15PhEOoC1 J._J\ 4 JL A 0 2 4 6 8 10 12 14 20 Figure 2.19. Low angle XRD data for c,,PhEo,c,. The samples were cooled from the melt and held at room temperture for ten to twenty hours before analysis. C13PhE07C1 C13PhEOGC1 C13PhE0501 C13PhEO4C1 intensity C18PhE0301 C13PhE020, A A 4‘ c,,PhEO,c, C18PhEOoC, M A A A. A I I 0 2 4 6 8 10 12 14 20 Figure 2.20. Low angle XRD data for CmPhEOyCl. The samples were cooled from melt and held at room temperture for ten to twenty hours before analysis. 67 M’u CzoPhEO7C1 AJI A AA A CzoPhE05C1 CgoPhEO4C1 AA A AA 1? 2 2 .E CzophE03C1 CzoPhE02C1 A A A A A 44A...— CzoPhEOoC1 I IH J A I I4 I 0 2 4 6 10 12 '14 2 0 Figure 2.21. Low angle XRD data for CmPhEOYCl. The samples were cooled from melt and held at room temperture for ten to twenty hours before analysis. 68 Table 2.6. Calculated X-ray d-spacings for CxPhEoy. Samples were cooled from the melt and held at room temperature for ten to twenty hours before analysis. x 0 1 2 3 4 5 6 7 14 44.77 50.36 39.49 * * 39.49 42.79 44.64 16 48.07 54.12 25.17 62.77 38.26 41.53 80.68 " 18 51.98 58.66 64.15 67.87 49.31 80.78 86.52 92.54 20 57.32 62.49 68.33 73.30 78.66 84.77 90.61 95.57 * The samples are liquid at room temperature. " Not synthesized. with the exception of CmPhEO4C1, which shows a depression in the d-spacing. The CMPhEoycl and CmPhEoyCl series do not show clear trends. There are variations in the intensity of the 001 peaks, especially in the CmPhEoycl series. Two explanations are offered. First, the deviations in intensity may be due to orientation effects. Most of the samples are waxy and it is difficult to obtain a homogenous powder. Second, some samples are prone to annealing at room temperature, and such samples can lead to polymorphism. Although most samples are quite stable, some are readily annealed. Annealing not only affects the thermal behavior of the compounds, but also alters the crystal structure. Figures 2.22 and 23 show XRD data for annealed samples from the x = 18 and x = 20 series. As shown in Table 2.7, the d-spacings decrease appreciably compared to the un- annealed samples. 69 C13PhE07C1 .4? 8 9. 'E ) C18PhE06C1 C13PhE05C1 A W 0 2 4 6 8 1O 12 14 2 9 Figure 2.22. Low angle XRD data for annealed CmPhEoyCl. The samples were annealed at 2 °C below their melting points for two to ten hours to the ultimate stable structure before analysis. 70 CzoPhEO7C1 J X10 II x 5 CgoPhEO5C1 g a 3 .E CgoPhEO4C1 4 J1 2__ Czoph503C1 J J o. A_ 0 2 4 6 8 1 0 12 14 Figure 2.23. Low angle XRD data for annealed CmPhEoycl. The samples were annealed at 2 °C below their melting points for two to ten hours to the ultimate stable structure before analysis. 71 Table 2.7. Calculated X-ray d-spacings for C,PhEO,. Samples were annealed at 2 °C below their melting points for two to ten hours until they reached their ultimate structures. X Y 0 1 2 3 4 5 6 7 l4 # # # * * # # # l6 # # # # # # 44.0 " l8 # # # # # 44.1 47.3 49.8 20 # # # 65.1 52.6 46.2 # 52.5 * Liquid at room temperature. " Not synthesized. # No appreciable changes observed. 3) Spectroscopic characterization Infrared (IR) and Raman spectroscopy provide complementary information about the solid-state structures conformations of CxPhEOyCl. The CzoPhEchl series was chosen for study because the compounds are stable at room temperature, and both quenched and annealed samples have single morphologies. The results from this group of compounds can be generalized to the other series. All samples were heated to 100 °C, quenched to —40 °C and allowed to anneal at room temperature for ten to twenty hours. Figure 2.24 shows the 700-1600 cm'l portion of the Raman spectra of CzoPhEoycl, the region where bands sensitive to the conformation of the C; and CIEOy segments are seen. Characteristic Raman bands at 1062, 1108, and 1129 cm’l indicate that the alkyl chains pack in an extended planar zig-zag conformation,43 while bands at 854, 864, 1283 and 1483 cm’I are consistent with a (PCT) conformation of the ethylene oxide segments.44 72 CzoPhE07C1 020131115060, CzoPhE0501 CzoPh 0401 a? g 02013115030, .‘é CZOPhEOZC, 02013115000, 700 900 1100 1300 1500 Raman shift (cm") Figure 2.24. Raman spectra of C,,PhE0,C,. The samples were cooled from the melt and held at room temperature ten to ten hours before analysis. 73 The Raman spectra indicate that the tendency to adopt a helical structure for the ClEOy segment appears as early as y = 2. In contrast, the ClEOy segments of CxEOy amphiphiles reported to date have planar zig-zag conformations when y < 4, with many structural variations at y = 3 and 4.38 2.3 Discussion 1 Conformation and solid-state structure The CzoPhEoycl series of compounds was used for structural studies because they show systematical changes in their thermal and structural properties, and trends seen in these compounds can be used to interpret data from related series of compounds. Structural studies of these compounds were aided by molecular mechanics calculations (Hyperchem). Because the resulting energy-minimized conformations are gas phase minima, the results were primarin used to assist in the interpretation of the IR, Raman and X-ray data. In the calculated conformation of CzoPhEO-7C1 (Figure 2.25), the C1E07 chain forms a 72 helix while the alkyl segment has the expected planar zig-zag conformation. In the calculations, the two side chains attached to the ring do not show cooperative effects. Thus, the conformation of the alkyl chain and the connection to the aromatic ring are identical for CgoPhEOoCI and CzoPhEO-ICl. As noted previously, the Raman data for the CzoPhEchl series are consistent with planar zig-zag conformations for the alkyl chains, and the trans, gauche, trans, conformation characteristic of a 72 helix for the ethylene oxide segments when y .>_ 2. Thus, the structures of the alkyl and ethylene oxide segments in CxPhEoyCl match those of the PE and PEO homopolymers. Seeing a trans, gauche, trans conformation for short ethylene oxide chains in crystalline materials was unexpected. Our previous work on the 74 Figure 2.25. The conformation of C2oPhEO1C1. The size and the shape of the molecules were calculated using Hyperchem. 0 is the tilt angle between the alkyl chain and the ethylene oxide axis. solid state structure of C,,EO,,Cx compounds showed that the E03, segments had planar zig-zag conformations for y < 7, which we attributed to packing constraints caused by the mismatch in the cross-sectional area of a helix relative to the planar zig-zag chain.39 One explanation for the appearance of trans, gauche, trans conformations in short CIEO, chains is that the tilted benzene ring that connects the C, and CIEOy chains provides the extra space needed to accommodate nonplanar CIEOy chains.”‘39 In crystalline PEO, each ethylene oxide unit in the 72 helix is 2.8 A in length.24'25'45 The experimental d- spacings of CmPhEoycl give a 5.6 A increment per ethylene oxide unit. The experimental d-spacing increment of CwPhEoyC; indicates a bilayer structure with the ethylene oxide unit in a helical conformation and packed normal to the surface. In the conformations calculated using Hyperchem, the axes of the C,‘ and CiEOy chains are offset by 15° as shown in Figure 2.25. Because the calculation neglects nearest neighbor 75 interactions, the angle may be different in the crystalline phase of the material. The actual tilt angle of the C, chain relative to the CnEOy axis was determined from the experimental d-spacing increments. Shown in Figure 2.26, are the experimentally determined d-spacings for the CxPhEOyCl compounds plotted as a function of the length of the CEO, chain. The line for the C2oPhEO,C1 series is the least squares-fit to the experimental d-spacings for C2oPhEOyC1. The lines for the ClgPhEOyCl, CmPhEoycl and CuPhEchl series were obtained by assuming that each C4H3 unit contributes 4.53 A to the measured d—spacing. This corresponds to the alkyl chains tilting 25° relative to the axis defined by the CIEOy chains.“5 The bilayer packing model fails for several samples in the C16 and C24 series, especially those with long CIEOy chains. These data indicate a different packing arrangement, which is discussed later. The lengths of the C2oPhEO,C1 molecules along the z-axis were calculated for a conformation where the alkyl chains are tilted. The theoretical d-spacings calculated from the molecular length and allowing 1.7 A of space between the molecular end groups are shown in Table 2.8.'6 The experimental data agree well with the calculated head to head packing arrangements as shown in Figure 2.27 for C2oPhEO7C1. Table 2.8. Low angle XRD d-spacings and Hyperchem calculated molecular length of the CmPhEO,C1 series of compounds. y 0 1 2 3 4 5 6 7 13:13:13? molecular 26.3 29.1 31.9 34.7 37.5 40.3 43.1 45.9 $333“) 56.2 62.1 67.7 73.3 78.9 84.5 89.9 95.3 $553222?) 57.3 62.5 68.3 73.3 78.8 84.9 90.6 95.6 76 100 80 '2": U) .9 § 60 an “O 40 ~ 20 l l l l I l l 0 1 2 3 4 5 6 7 No. of ethylene oxide units Figure 2.26. d-spacings of C,,PhEOy vs.C1EOy length. (0) C2oPhEOyC1, (A) CuPhEoyCl, (I) CmPhEOyCl, (O) CuPhEOyCl. Unfilled symbols correspond to annealed samples. 77 95.3 A vertical gap 1.7A d-spacing Figure 2.27. The lamellar structure formed by bilayer packing of C2oPhEO7C1. The calculated d-spacing (Hyperchem) is 95.3 A. 2 Stepwise crystallization A complete understanding of the nanometer scale structure of these amphiphiles requires some knowledge about the details of the crystallization mechanism. A stepwise crystallization process where the Cx and CIEOy segments crystallize independently is proposed for these compounds. For the case of infinitely long PEO and PE chains joined by a single benzene ring, the immiscible PE and PEO chains should have the conformations and crystallization behavior typical of the pure homopolymers, modified to a small degree by the junction between the chains. Thus, each phase will crystallize independently. In the short chain limit, the junction between the chains is large relative to 78 the chains and the chains are too short to lead to phase separation. These materials should form isotropic melts and crystallize as single entities, molecule by molecule. We believe that the amphiphiles described here are situated near the borderline between these two cases. A property of PEO tends to emphasize step-wise crystallization in the CxPhEOyCl amphiphiles. Unlike PE, whose favored conformation is clearly planar zig-zag, the planar zig-zag and helical structures of PEO are almost equivalent in energy, with the helix favored in the solid state due to dipolar interactions with neighboring PEO chains. Under tension, PEO has been shown to adopt a zig—zag conformation in the solid-state, and relax to the helical structure once the tension is released. Thus, PEO is prone to super-cool and form disordered solid state structures because of these energetically similar conformations.46 Combined DSC and IR data provide evidence that the relatively short C" and CIEOy chains behave independently during heating and cooling. Figure 2.28 shows a DSC run for C2oPhE05C1, which shows the multiple thermal transitions in heating and cooling scans that are typical of the C2oPhEO,C1 series. The sample was heated to 100 °C to erase its thermal history, quenched at 200 °C/min to —40 °C, and then was heated at 10 °C/min to 100 °C, held for l min, and cooled to —40 °C at 10 °C/min. IR spectra (Figure 2.29) were taken at the points labeled with arrows, while the Roman numerals correspond to the structures sketched in Figure 2.30. Cooling from the melt leads to crystallization of the alkyl portions of the molecules. The exothermic transition at 42 °C in the cooling curve is the heat of crystallization for the alkyl benzene portion of the molecule. The IR spectrum (Figure 2.29) taken at point II in Figure 2.30 has weak peaks at 1323 cm'1 and 985 cm'1 that 79 Gov 9293:.2 dad 2sz E :32? $88: :osmfizfimbo 0&3:on 2: .8 momma 2.28:: 05 9 Home: :mfiw 2: :0 23:5: 580% on... :83 203 88on M: 20:? 3:6: 8865 $65 2? :UmOmEmSU we mcaom UmQ 2:. .wN.N unawE mv- mm mm mm mm mr m- mm- 9508 = Illlv E Ff o . m 93ch 0 m3: u _ mczmoc 2 .II E :— nococmza =9: 0° mm B nmfimccm <— opue ‘Mou 19914 80 hold at 44.5 °C (annealed) hold at 35 °C (IV) 1 I". J \ ll 1 \ slow heat to 35 °c (111 to IV) I f f; l \ [/1 \ - \. \ H I! \v [’41: J/ J V\/J ,\\""‘“//\\-~J'/f\m"‘\ ’1 \c—vsoy- quenched sample (ll) absorbance melt sample (I) reference CzoPhEOo l l l L 1 600 1400 1 200 1 000 800 600 wavenumber (cm") Figure 2.29. IR spectra of C2oPhE05C1 taken at various temperatures. The Roman numerals correspond to the DSC scan of Figure 2.28. 81 II, V '36 SE 01 199H I). 001 01 19:11 Cool to 10 °C. Figure 2.30. Stepwise crystallization of C2oPhE05C1. The Roman numerals correspond to the DSC scans of Figure 2.28. The C20 chains are shown in light gray, the C1E05 segment in dark gray, and the phenol ring in black. 82 correspond to the disordered ethylene oxide chain conformations seen in liquid state samples,“47 while strong peaks at 1468 cm'l and 721.5 cm'1 indicate ordered planar zig- zag alkyl chains.48 Slowly heating the quenched sample to 35 °C allows the ethylene oxide segments to reorganize into the more stable helical structure (Figure 2.30, IV). Strong peaks at 1146 cm", 1115 cm'1 and 853 cm'1 correspond to a well-packed helical structure of the CIEOy chains.49 Heating to 44.5 °C melts the lattice of the ClEOy chains (Figure 2.30,V). Further heating through the higher melting transition melts the alkyl chains (Figure 2.30, I). Stepwise crystallization was further verified by comparing the heat of crystallization seen in DSC cooling scans for the CmPhEOyCl and C2oPhEO,C1 series with the weight fraction of alkylbenzene portion of the molecule (Tables 2.9). The linear relationship of both plots (Figure 2.31) and the observation that alkyl chains of the same length have the same heat of crystallization prove that the transition is due to crystallization of the alkylbenzene portion of the molecule. Figure 2.32 shows scans of C2oPhE05C1 that provide further evidence for step-wise crystallization and our assignments for the thermal transitions. The DSC heating scan (top) shows structure below 30 °C that we attribute to crystallization of the PEO chain segments, followed by two melting transitions, one for the PEO segments and the higher transition for melting of the alkylbenzene portion of the molecule. If a cooling scan is stopped at 30 °C, just after the crystallization of the alkylbenzene segments and above the transitions assigned to PEO crystallization, then heating results in a single melting peak that matches the position and intensity of the higher melting peak seen in the original scan. 83 A plot of the C2oPhEO,C2 melting points as a function of the CIEOy length (Figure 2.33) shows that similar behavior is seen for y > 2. Double melting points are common, with the alkylbenzene melting points (0) declining and the CEO melting points (X) increasing with an increase in the CIEOy chain length. The melting points of the CEO, and C, chains tend to merge at high values of y, but the crystallization temperatures of the C1,; to C20 compounds remain widely separated (Figures 2.10-2.12). Decreasing the alkyl chain length causes the melting points to merge at shorter CIEOy lengths (lower temperatures), and as shown in Figure 2.34, the ClgPhEoyCl series gives a single melting point at y = 5. Table 2.9. Alkylbenzene weight fraction and heat of crystallization for the CmPhEOy and C2oPhEOy series. y Alkylbenzene weight fraction AH (crystallization) (J/g) CmPhEOy CzoPhEOy ClgPhEOy C2oPhEOy 2 0.75 82.5 3 0.669 0.687 72.0 75.5 4 0.614 0.633 66.7 72.9 5 0.567 0.587 62.6 69.2 6 0.527 0.548 55.4 66.5 7 0.493 0.513 52.8 62.0 84 AH (Jlg) 90 50- l L l 4O 1 l a l 0.4 0.5 0.6 0.7 0.8 alkylbenzene weight fraction Figure 2.31. Alkylbenzene weight fraction vs. heat of crystallization for (A) ClsphEchl and (O) CzoPhEchl. 85 second heating scan second cooling scan ‘— heat flow, endo third heating scan l I l l -1 O 1 0 30 50 70 90 temperature (°C) Figure 2.32. Stepwise crystallization of CzoPhEOscl. The second heating scan was aquired from a sample quenched from melt. The second cooling scan was stopped at 30 °C, and held for one minute before the third heating scan started. 86 temperature (°C) 65 $ single melting points 5. - i Q melting point of annealed sample 0 O - 0 double melting points . X X \' X 35 - x X 25 l l I J I I l 0 1 2 3 4 5 6 7 No. of ethylene oxide units Figure 2.33. Melting points of the C2oPhEOyC1 series of compounds. 87 temperature (°C) 55 4:5 0" O) 01 25 single melting point i @ melting point of annealed sample 0 O O G 29 G . 0 O 6 double melting points ‘4 A A O 1 2 3 4 5 6 7 No. of ethylene oxide units Figure 2.34. Melting points of the ClsPhEOyC, series of compounds. 88 3 Effects of annealing on structure Since crystallization is often under kinetic control, the overall structure obtained by cooling from the melt may not be the most stable product. Annealing often converts these kinetic products to a more thermodynamically favored structure. Some compounds can be easily annealed by holding them a few degrees below the melting point for several hours. C13 and C20 compounds with long C1130y segments show systematic changes in their DSC curves after annealing. Figures 2.15 and 2.16 compare the DSC traces for the quenched and annealed samples of those compounds. For y > 4 annealing results in a single, higher melting transition with a heat of fusion larger than the combined melting peaks of the quenched sample. Figures 2.33 and 2.34 compare the melting points of the annealed and quenched samples. The changes in chain conformation caused by annealing were studied by Raman and IR spectroscopy. Figure 2.35 shows the Raman spectra of quenched and annealed samples of C2oPhE05C;. Both spectra indicate a planar zig-zag conformation for the alkyl chain and a helical conformation for the ethylene oxide chain. The distortion of the 854 and 864 cm’1 bands in the 44.5 °C annealed sample may be due to distortion of the CIEOy 72 helix. XRD (Figures 2.22 and 2.23) indicates a change in the nanometer-scale structure of the lamellae. The molecules still pack in layers, but the d—spacings are smaller than for the quenched samples listed in Table 2.7 . A plot of quenched and annealed sample d- spacings (Figure 2.27) reveals a clear trend. Most annealed samples (y > 4) fall into one region of the plot and show systematic increases in d-spacings with increases in the 89 89:88 208: 88: ON 9 2 :8 6.. mm-_mv 2:88:82 809 8 20: 2:83 8 8882 3:850 83 88809. 8289 08 880:? .830: m :8 05 03V 8 380:8 28 :08 808 88:05: 0883 8 80¢ 3:850 83 88.8% :9 2E. ._UnOmE.—80 8 88% 883— .mm.~ 0.53m A783 8:83:88; com com 00.. P com? com P u u q q 058..an9 Eco. 88 29. 88 82083 eoueqiosqe 0... Q3 8 88688 98 850835 90 length of the CIEOy chain. The line drawn through the experimental points is a least squares-fit to the annealed CmPhEchl data, which give a 2.86 A increment per ethylene oxide unit. This indicates that distorted 72 helices of ethylene oxide units interdigitated and pack normal to the surface. The increment that gave the best fit to the C20, C15 and C14 data was 2.5 A per C2H4 segment, which corresponds to a tilt angle of 0°. The experimental d-spacings for the annealed samples are one benzene ring (4.7 A, Figure 2.25) larger than the calculated molecular length assuming that the C, and CIEOy chains share the same C 1 axis. This indicates that the structure of the annealed samples is a fully interdigitated structure with the molecules packed normal to the surface as shown in Figure 2.36. Upon annealing, the C, chains retain their planar zig-zag conformation and CIEOy chains are helical. The tilt angle of the C, chain changes from 25° to 0° relative to the CIEOy axis. The disappearances of a peak at 1419 cm'land minor variations around 1210 cm'1 in the Raman spectra (Figure 2.35) are due to the conformation changes of the bonds between the benzene ring and ethylene oxide chain because no such peaks are reported for related compounds C,EOy and C,EO,C, shown in Scheme 2.1. Several unannealed CmPhEOyCl and C14PhEO,C1 samples fall into the same region of the plot shown in Figure 3.26, suggesting that they have similar structures. An examination of their DSC plots shows that it should not be surprising that the quenched CuPhEoyCl and CmPhEoyCl series of compounds have the same structure of the annealed ClgPhEoycl and C2oPhEO,C1 series of compounds. The cooling scans of ClgPhEOyCl and C2oPhEOyC1 (Figures 2.11 and 2.12) support the step-wise 91 crystallization pattern, i.e. the alkyl benzene portion of the molecule crystallizes first and determines the structure of the quenched sample. In contrast, the cooling scans for CuPhEoycl and most samples of the CloPhEOYCl series (Figures 2.9 and 2.10) show that the C, and CIEOy side-chains crystallize concurrently. Thus, the step-wise crystallization scheme breaks down for short C, lengths and the more stable interdigitated structure is directly formed by quenching. One could argue that even if the C14PhEO,C1 series forms metastable bilayers, the shorter carbon chains may not be able to stabilize the bilayer structure at room temperature, and annealing will rapidly convert the bilayer structure to the interdigitated form. Some compounds have experimental d-spacings that fall outside the two main groups. The structures of these compounds are not yet known, but could result from tilting of the interdigitated or bilayer structures. d-spacing Figure 2.36. A fully interdigitated packing structure of CzoPhEO-lcl. 92 2.4 Conclusions A series of exact length oligoethylene oxide monomethyl ethers were synthesized and used for the preparation of amphiphilic materials (C,PhEO,C1) with exact side chain lengths. In compounds with long alkyl chain (x = 18, 20) the ClEOy and C, side chains melt and crystallize from the melt via a step-wise mechanism. The C, chains crystallize first and adopt a planar zig-zag conformation, while the CIEOy chains adopt a helical conformation. In most cases crystallization of alkyl chains leads to a bilayer structure where both the alkyl and ethylene oxide chains are aligned normal to the surface of the layers, and the alkyl chains are titled 25° relative to the surface normal. Annealing converts the bilayer to the more stable interdigitated structure with both chain aligned normal to the surface. In this chapter, we described how amphiphilic side-chains determine the nanometer scale structures of amphiphilic molecules. The side-chains align the benzene ring that links the chains, opening a new route to ordered nanometer scale materials. In the next chapter, we examine amphiphiles that contain benzene rings with strong dipole moments. We will find that that the tendency for the CIEOy and C, chains to align in separate domains can be used to overcome the usual pairing of the dipoles, and yield a net alignment of the dipoles. This opens a new route to arrays of stable molecules with aligned dipole moments. 93 2.5 References (l) Likharev, K. K. IBM J. Rex. Dev. 1988, 32, 144-158. (2) Likharev, K. K.; Claeson, T. Sci. Am. 1992, 80-85. (3) Reed, M. A. Sci. Am. 1993, 118-123. (4) Vijayakrishnan, V.; Chainani, A.; Sarma, D. D.; Rao, C. N. R. J. Phys. Chem. 1992, 96, 8679-8682f. (5) Evans, C. C.; Bates, F. 8.; Ward, M. D. Chem. Mat. 2000, 12, 236-249. (6) Bates, F. S. 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Phys. 1964, 41, 2902-2911. 96 CHAPTER 3 Dipole Alignment via Phase Separation of Amphiphilic Side Chains 3.1 Introduction The field of nonlinear optics (NLO) is concerned with the interaction of electromagnetic fields with a medium, generally in the optical frequency range, resulting in the alteration of the phase, frequency, or other propagation characteristics of the incident light.I The most important and useful NLO effects are 2"d—order phenomena, which are observed when light is passed through a noncentrosymmetric medium. This effect was first observed in l96lwhen laser light was passed through an air quartz interface. Besides the laser beam, a faint second beam was observed, which had twice the frequency of the incident light. This frequency doubling effect is called second harmonic generation (SHG). Until the discovery of blue laser sources in the 808, SHG from materials such as potassium dihydrogen phosphate (KDP) was the major source of UV laser light.2'3 SHG is also used to measure the 2"d-order NLO response of NLO materials. Another important 2"d-order NLO phenomenon is the electro-optic (BO) effect, in which the refractive index of a material is controlled through the application of an external electric field. Since 2"d-order NLO materials can be used to manipulate the phase and frequency of the incident light, they have important applications in laser optics. EO modulators can be used to encode electrical signals onto fiber optic transmission lines as one component of all-optical processing. Recently, the Dalton group reported new polymeric EO modulators operating at 110 GHz with a half-wave voltage of 0.8 volts.4 Figure 3.1 shows the major 2"d-order NLO effects seen in materials.1 97 2"d-order NLO material 1 —-—->‘ 20) . _ a) > Second harrnonrc generation —> (1): (On ———> 3 . . Parametric am lification Incrdent lrght (”b a)” p Rotate polarization Electrooptic Pockels effect Diffraction Figure 3.1. The major types of 2"°-order nonlinear optical (NLO) effects.l 98 Inorganic crystals such as KDP and lithium niobate (LiNbO3) have high nonlinear responses and stable physical properties, and these materials dominated nonlinear optical technology. Before the 1970s, there were few systematic investigation of new materials that were especially designed for efficient nonlinear optical interactions, and there were only isolated examples of experimental studies on organic materials, such as benzopyrene5 and hexamethylene tetraamine.° At the end of the 19608, a semiquantitative testing procedure called the Kurtz Powder Technique was developed which led to rapid screening of powder samples for SHG activity. Another technique, the Maker fringe method, enabled researchers to fully characterize the NLO properties of single crystals.7‘8 In 1971, Davydov established the connection between enhanced nonlinear activity and charge transfer in conjugated molecules.9"° This changed the area of organic NLO from merely random testing of materials to a real scientific research field. These early studies showed that the NLO response of nonlinear organic materials can be at least ten times larger than that of inorganic crystals. This stimulated considerable work in molecular engineering during the 19705 to design organic NLO materials based on the understanding of structure-property relationships.I "'3 The development of fiber optics for data transmission, and rapid developments in telecommunications and computing have resulted in the need for improved photonic components such as low-loss, inexpensive optical waveguides and very high bandwidth integrated optical modulators. Polymeric 2"d-order NLO materials are especially promising for modulators, because the polymers can be easily spin coated onto substrates and polymeric modulator structures can be fabricated using standard photolithographic 99 techniquesws Therefore, research on defining noncentrosymmetric arrays in polymeric materials has been very active. 1 Origins of 2"d-order NLO of organic chromophores When an electric field E interacts with the charge distribution of a molecular system, the interaction produces a force that causes displacement of the electron density, which results in an induced dipole 1.1. For small fields, the induced dipole is linearly proportional to the applied field (see Equation 3.1). 113"“ = a,-,-E,~ Equation 3.1 When a molecule is subject to a high intensity electric field such as found in a laser beam, the induced polarization becomes a nonlinear function of the field strength, which can be expressed by expanding the total dipole as a Taylor series (see Equation 3.2)16 where u is the permanent dipole, or the linear polarizability, B the second-order polarizability and y the third-order polarizability. The terms beyond OLE are not linear in E and are referred to as the nonlinear polarization, which gives rise to nonlinear optical effects. For centrosymmetric molecules, [3 = 0, and thus a noncentrosymmetric molecule is required for 2“d-order polarizability.I4 11,-: 14° + a.-,~Ej +(1/2)8,,-,.E,E,, + (1/6)y,-,-k,E,-EkE,+ Equation 3.2 Similar to the molecular level, the bulk polarizaton is given by Equation 3.3.'7 P = P0 + 2%: +(1/2) x‘Z’EE + (1/6) x‘3’EEE + Equation 3.3 A nonisotropic array of molecules is required for a 2"d-order nonlinear response. Both Equations 3.2 and 3.3 indicate that the nonlinear polarization becomes more prominent with increasing field strength. Under normal conditions OLE > [382 > 7E3, so a strong field is required for a strong NLO response. '4 100 —— applied field _.........-.. induced polarization o - x/ \ > to [1 t2 time A charge distribution t0 t] - 1:2 i l 1 F to 11 [2 time induced polarization B Figure 3.2. A) Plots of the electric field of an a plied light wave and the induced polarization wave as a function of time for a 2 -order NLO material. B) Diagram depicting the charge distribution and the polarization in the material as a function of time.18 101 \ /\ f v \/ second 'W \ /\ /\ /\ /\, V V V V \ /\ f V V Figure 3.3. The asymmetric induced polarization can be decomposed into a direct current (DC) component and components at the fundamental and second harmonic frequencies. '8 DC component time 102 The second order nonlinear response of a noncentrosymmetric system is demonstrated in Figure 3.2.'8 Application of a sinusoidal oscillating electric field leads to an asymmetric oscillating induced polarization, which is stronger in one direction and weaker in the opposite direction. This induced polarization can be decomposed into a direct current (DC) component and components at the fundamental and second harmonic frequencies as illustrated in Figure 3.3.'8 Since the 2"d-order NLO response requires a nonisotropic array of noncentrosymmetric molecules, this is achieved in practice by aligning molecules with strong dipoles in a matrix. p—Nitroaniline derivatives, organic dye molecules and molecules with extended conjugation and having electron donors and acceptors at opposite ends of the conjugated segment are ideal candidates. Molecules that contain extended 1: systems with charge asymmetry have high dipole moments and extremely large values of [3.1942 The high molecular dipole moment hinders macroscopic alignment of dipole moments, because electrostatic intermolecular interactions from the dipoles can extend over considerable distances (> lnm). At modest concentrations of chromophores (20% by weight), the chromophore-to-chromophore distance is within 1 nm and the dipoles couple in antiparallel fashion to reduce the total energy of the system. The effect of intermolecular electrostatic interactions among chromophores is to favor an overall centrosymmetric ordering of chromophores, unless other molecular interactions prevent chromophores from pairing.23'2° 103 2 Noncentrosymmetric array of chromophores 1) Organic crystals Organic crystals with NLO chromophores crystallized in an asymmetric unit cell could process high 2"d-order NLO effects. These compounds have been studied since the 1960s‘5'u'27 primarily by powder SHG using the Kurtz powder technique.28 Many new compounds have been synthesized,”30 with most successful being N—(4-nitrophenyl)-L- prolinol (NPP).3 ‘ The general approach toward the synthesis of crystals with large second order susceptibilities is to create a chiral center within the molecule, because a single enantiomer can only crystallize in an asymmetric unit cell structure. Although crystalline organic NLO materials have higher NLO responses than inorganic crystals (e. g. LiNbO3), the application of organic 2"d-order NLO materials is limited because of their low melting points, low chemical stability, the difficulty in growing large crystals and processing problems. Thus it is crucial that the mechanical and physical properties of organic 2'”- order NLO materials be improved. 2) Poled polymer films A promising new approach, electric field poling of polymers that contain 2'”- order NLO chromophores, was developed by Meredith in the early 19808.32'33 The key idea of this approach (demonstrated in Figure 3.4) is to incorporate an NLO chromophore with a high susceptibility (usually an azo dye) into a polymer matrix and heat the polymer to above its glass transition temperature (T3). Application of a large electric field aligns a portion of the dipoles, and cooling to below T8 with the electronic field in place freezes the chromophores in an acentric microstructure. In this way, the poled material has a net dipole moment and the polymer is an active 2"d-NLO material. 104 ++++++ ........ electric field A B C 9 chromophores W polymer chain Figure 3.4. Electric field poling of a guest-host system. A) Chromophores oriented randomly into the polymer matrix. B) Heating the polymer system to above its glass transition temperature (T g) in an electric field aligns the chromophores. C) Cooling to below T3, locks the chromophores in the aligned state.”36 105 Several strategies have been developed to deal with dissolving chromophores into the polymer system and stabilizing the aligned chromophores. In a guest host approach the chromophore is simply dissolved into the polymer matrix, aligned by poling and cooled below the T8 of the polymer to freeze the chromophores in place.“36 Cross-linking may be used to further stabilize the guest chromophores.”38 In the functionalized chromophore approach, chromophores are chemically bonded to the polymer chains so as to increase both the solubility and stability of the aligned chromophores in the polymer system.35'39'42 Compared to organic crystals, polymeric 2"d-order NLO materials have high NLO responses with improved physical properties. Recently published results indicate that chromophores aligned in a polyamide system with a Tg of 313 °C have no observable decrease in the nonlinear response after 1000 hours at 100 °C.“44 Polymer NLO materials are the material of choice for future applications since they can be easily processed and integrated into semiconductor-polymer optical circuits. They also have a lower dielectric constant than inorganic NLO materials, which makes them superb candidates for very high frequency optical modulators.45 Although poled polymers are very attractive, there are fundamental drawbacks of this system. First, it is thermodynamically unstable,46 with relaxation times that range from several days to months depending on the polymer system. A steady decrease in the NLO susceptibility would be incompatible with their application in permanent devices. Secondly, the chromophores in poled polymers are poorly aligned. The alignment of dipoles is rather a statistical phenomenon than the full alignment of individual molecules.36 The overall alignment of the chromophores in poled polymer films ranges 106 from 8% to 30% depending on the poling methods and properties of the chromophores and polymer systems.34'36'47 Aggregation is common at higher concentrations (20% by weight) of chromophoreszf"48 Recent developments are addressing these problems. Jen introduced large groups to chromophores to make the aggregation of the chromophore molecule less energetically favorable.49 Dendritic chromophores have also been used to solve the aggregation problem.50 Dalton recently described a tetrablock main chain NLO polymer as an approach to thermodynamically stable 2nd-order NLO materials.5 ' The structure of the four blocks favors an overall noncentrosymetric alignment of the dipole moments. The Bates group also investigated complexes of p-nitroaniline derived chromophores and block copolymers.52 Both the Dalton and Bates approaches try to harness the phase separation of block copolymers to stabilize aligned chromophores in the bulk state. 3) Layer by layer assembly Chromophore alignment can also be achieved through layer-by-layer construction (Figure 3.5). Two major techniques have been used. One approach is the synthesis of acentric Langmuir-Blodgett (LB) films,53 while the other involves chemical bonding of adjacent layers using metal-phosphonates.54’55 Both approaches lead to highly ordered arrays of chromophores, but both have limitations. LB films are derived from relatively weak van der Waals forces, and thus they are neither thermally stable, nor can persistent order be maintained indefinitely in multilayer assemblies.56 Metal-phosphonates have robust physical properties, persistent structural anisotropy and thermal stability, but the layer by layer assembly process is slow and the overall order is sensitive to defects. Because the regularity of each layer is controlled by the fidelity of the previous layer, 107 N onpolar tail Chromophore Polar head Figure 3.5. Schematic of the layer by layer construction of aligned chromophores by the Langmuir-Blodgett technique.”55 defects in a layer will propagate to the higher layers. Up to 40 regular layers have been deposited using strictly controlled conditions.57 The high regularity of dipoles compensates for the limited volume fraction of chromophores in LB and metal phosphonate systems. In the research described in this chapter, we investigated whether the tendency for phase separation seen in diblock oligomers can be used to align chromophores and produce thermodynamically stable 2"d-order NLO materials. In CHAPTER 2, it was shown that the diblock oligomers C,PhEO,C1 adopt a lamellar structure due to phase separation of the alkyl and ethylene oxide chains. If the benzene ring is chemically modified to give a p-nitroaniline NLO chromophore, it will potentially disturb the lamellar structure. The use of p-nitroaniline as the NLO chromophore has many advantages. Its size is close to that of benzene, and the structure of p-nitroaniline is fully characterized and well documented (Figure 3.6).58‘59 It crystallizes as head to tail chains due to strong H-bonding between neighboring nitro group oxygens and amino hydrogens. 108 Projection of the structure along the b axis. Paired structure unit Figure 3.6. P21/c space group of the p-nitroaniline unit cell and the antiparallel arrangement of the paired structural unit.”59 109 The chains pack in layers in an antiparallel fashion due to strong dipole-dipole interactions, effectively canceling the net dipole moment of the crystal. Diblock copolymers where the volume fractions of each block are near 0.5 adopt a lamellar packing structure.60 Thus C,PhEO,C1 compounds which have equal length C, and CIEOy chains thermodynamically prefer a lamellar structure. Replacing the Ph group with a p-nitroaniline group will introduce dipole — dipole interactions as well as H- bonding into the system. These changes may alter the lamellar structure. The competition between the tendency for the diblock to phase separate and the pairing energy of the dipole moment will determine the final structures of the compounds. 3.2 Results 1 Material synthesis 1) Acronyms for the compounds The compounds synthesized in this chapter have the C,PhEO,C1 basic structure, but with a chemically modified Phi ring. The acronyms used for the compounds follow the naming protocol of the C,PhEOyC1 series with slight modifications. When C,PhEO,C1 is substituted at the 2 and 5 positions with amino and nitro groups, the products are abbreviated as C,PhNEO,C1, where N refers to a benzene ring substituted at the 2 and 5 positions with the amino and nitro groups. Since the substitution pattern is identical for all members of the series, it is not explicitly noted in the acronym. An example of the naming protocol is shown in Scheme 3.1. The dimethylated versions of C,PhNEO,C1 are simplified as C,PhNC2EO,C1. The compound with decyl chains at the 2 and 5 position of p-nitroaniline is simplified as CmPNAClo, where PNA refers to the p- 110 Scheme 3.1. Examples of acronyms for compounds NH2 CH3(CH2)x-1 O 0(CH20H20NCH3 02N C,PhNEOyC1 N(C H3)2 011mm,),1 O O(CH2CH2O)yCH3 O2N NH2 CH3(CH2)9 0 (0112190113 02N CmPNACw 111 nitroaniline core and C10 refers to the decyl side chain. The positions of the decyl chains on the p-nitroaniline are omitted in the acronym. 2) Synthesis of C,PhNEO,C1, C,PhNC2EO,C1 and CloPNACm Direct nitration of C,PhEO,C1 failed. The reactions gave low yields with numerous difficult to separate byproducts because the link between the phenol oxygen and the ethylene oxide chain is not stable under nitration conditions. Thus, the synthesis of C,PhNEO,C1 follows Scheme 3.2. The phenol starting materials were made according to the procedure described in CHAPTER 2. Nitration of the alkylphenol gave 9 and a byproduct with the nitro group meta relative to the OH group. These two isomers were readily separated by column chromatography. Intramolecular H-bonding between the phenol and the oxygen of the nitro group in 9 prevents H-bonding with the silica gel during flash chromatography, thus the Rf value of 9 is higher than that of the meta product. The ClEOy chain was introduced onto the benzene ring followed by reduction of nitro group by catalytic hydrogenation. The amino group was then protected by reaction with acetic anhydride. Both the reduction and protection steps are clean reactions with nearly quantitative yields. Since the benzene ring of 12 is activated by the EO,C1 and amide groups, nitration using a mixture of sulfuric and nitric acid at —15 °C is complete in less than five minutes. The fast reaction and low temperatures prevent significant degradation of the CIEOy chain. Since the amide is a better para directing group than an ether,“62 the major product of the nitration was 13. Chromatography was used to separate 13 from the byproducts. Extreme care was needed for successful separation. Product 13 and other byproducts have very similar Rf values because the polarity of the products is largely determined by the CIEOy chain when y is large. Removal of the acetyl 112 Scheme 3.2. Synthetic route to C,PhNEO,C2. OH HNO3 (70%) glacial acetic acid 0 ——-> (CH2)x-1CH3 6 (CH2CH2O)yCH3 I NHCOCH3 (CH2)x-1CH3 '12 HN03 (70%) H2304 (COIL) glacial acetic acid 0 (C H2O H20)“: H3 l NHCOCH3 (CH2)x-1CH3 02 13 H 0 N02 NaH/THF/DMSO (C l'1'.?)x-1C1'13 O(CH2CH2O)YCH3 TSO(CH20 H20)YCH3 N 02 (Cl—'2)» tcHS 1O Flaney nickel ethanol O(CH2CH2O)yCH3 acetic anhydride ‘ O (CH9,.1CH3 11 O(CH2CH20)yCH3 NaOH, H20 NH2 01450, 80 °C 0 ’ O2N (CH2),.1CH3 14 CxPhNEOyc1 113 group gave 14 (C,PhNEOyC1), which was purified by chromatography and recrystallized from ether. The purification conditions and physical properties of compounds 9-14 are summarized in Table 3.1. Product 14 was reacted with methyl iodide to give the dimethylarnino derivative (Scheme 3.3). The reaction must be limited to less than 30 min to avoid formation of the ammonium salt. The salt is easily removed from 15 via chromatography. Scheme 3.3. Synthetic route to dimethylated C,PhNC2EO,C1. O(CH2CH2O)yCH3 CH3! O(CH2CH2O)yCH3 NH2 KOH N CH O omso O ( W ————> 02 02 (CH2)x-1CH3 ( H2)x.1CH3 14 ‘5 C,PhNC2EOyC1 A nitroaniline with two alkyl chains (CmPNACm) was synthesized following the procedure shown in Scheme 3.4. Since there is no CIEOy chain, the dialkylated benzene can be directly nitrated and purification of the intermediate and final products is relatively simple. 114 Scheme 3.4. Synthetic route to CloPNACm. (C H2)9C H3 8 r CH3(CH2)9MgBr HN03(70%) (dppp)C12Ni/I’HF glacial acetic acid 0 ——» o ——» Bf (CHQQCH3 16 (C I"'12)90H:1 . . acetic anhydnde NHAC 60 °C 0 < ( H990 H3 1 9 HN03 (70%) H2804 (con.) glacial acetic acid (CHQQCHa NaOH, H20 NHAc omso, 80 °c O > 02 O2 (CH2)90H3 20 115 (011990143 I N02 (CH2)90H3 17 Raney nickel ethanol l NH; (C H2)90H3 18 (C HQgCHa l NH2 (CHQQCHa 21 C10PNAC10 116 N. H mm - 2 3o 83 E 86 2 ”mm om u x 0 H % mo - mm :6 Chem 05 mod 2 ”mm 2 u x m H % o2 - on 2.0 005? 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MO OSQUGOU |l7 2 Properties of C,PhNEO,C1 1) Single crystal X-ray diffraction Single crystals of compounds ClPhNEOoCl, CzPhNEOocl and C7PhNE02C1 were successfully grown from solution and their structures were determined by single crystal X-ray diffraction. Increasing the length of the side chains makes the compounds waxy, so growing crystals suitable for single crystal X-ray diffraction is more challenging. All three single crystals were grown and characterized by single crystal X- ray diffraction using similar conditions. Compound ClPhNEOoCl is used as an example. ClPhNEOoCl (0.1 g) was dissolved in 5 mL of ether, and transferred through a 0.5 pm syringe filter to a small vial. During a period of 20 hours the solution was slowly cooled to —40 °C in a vibration-free environment. A few yellow needle like crystals precipitated from the solution. The crystals were removed using a small glass fiber and examined under a microscope to be sure the crystal were of good quality. A crystal having approximate dimensions of 0.1 x 0.2 x 0.2 mm was selected and mounted on a glass fiber. All measurements were made on a Rigaku AFCSR diffractometer with graphite monochromated Cu-Ka radiation 01. = 1.54178 A) and a 12 kW rotation anode generator. ClPhNEOoCl adopts a triclinic unit cell structure with a = 7.472 A, b = 16.467 A, c = 7.162 A, a = 94.4l°, B = 100.04° and y: 82.04°. The space group was determined to be P-l with a goodness of fit indicator of 5.36 and an R factor of 0.059. The unit cell structure with views from the 100, 010 and 001 planes is shown in Figure 3.7 . CzPhNEOoCl adopts a monoclinic unit cell structure with a = 9.690 A, b = 17.329 A, c = 11.373 A and B = 95.02°. The space group was determined to be P21/a with a goodness of fit indicator of 2.84 and an R factor of 0.041. The unit cell structure with views from the 118 100, 010 and 001 planes is shown in Figure 3.8. Both ClPhNEOoCl and CzPhNEOoC, crystals have a pseudo anti-parallel structural unit of two molecules stacked on top of each other (Figure 3.9). This structural feature is due to the strong dipole-dipole . . ,4 .49 interaction between the molecules.26 8 The crystal structure of CyPhNEOzCl also was determined but with less accuracy. The molecular structure is shown in Figure 3.10. The molecules are no longer paired since increasing the length of the amphiphilic side chains disturbs the paired structure. The alkyl chain adopts a planar zigzag conformation, whereas the ethylene oxide chain is helical. The anisotropic displacement parameters of the last two atoms on the end of ethylene oxide chain (C18, 05) are off-scale, as indicated by the large ellipsoid drawings. Because the C1EOy chain prefers a helical structure, the conformation of the chain end is less consistent in the crystal, which affects the overall structure determination. The crystal system was determined to be a monoclinic unit cell with a = 25.258 A, b = 4.730 A, c = 33.104 A and B = 92.69°. The space group was determined to be C2/c with a poor goodness of fit of 7.44 and an R factor of 0.092. Single crystal studies of the rest of the series of compounds gave worse results than were obtained for C7PhNE02C1, and thus powder X-ray diffraction was used to elucidate structural information for the remaining compounds. 2) Powder X-ray diffraction Since suitable single crystals couldn’t be grown for compounds with long chains, We relied on powder XRD to elucidate their structures. Low angle XRD data can provide some information on the nanometer scale structure of the material. For example, a well- defined series of 001 lines indicates a layered structure whose spacing may be calculated 119 View from the 010 plane View from the 001 plane Figure 3.7 . Unit cell structure of ClPhNEOoCI. 120 View from the 010 plane View from the 001 plane Figure 3.8. Unit cell structure of CzPhNEOocl. 121 ClPhNEOoCl CzPhNEO.C1 Figure 3.9. Paired solid state structure of ClPhNEOocl and CzPhNEO.C1. 122 Figure 3.10. Solid state structure of C7PhNE02C1. using the Bragg equation (Equation 2.1). Before taking XRD measurements, all samples were heated to ten degrees above their melting point for 5 minutes and left at room temperature to crystallize overnight before the XRD run. . Figure 3.11 shows XRD scans of the CxPhNEO,C1 series. The intensities of each scan were normalized by setting the major peak of each scan to the same intensity. Three characteristic types of XRD plots were found. ClPhNEOoCl and Cd’hNEOoCl show scattering typical of small molecule unit cell arrangements. The CloPhNEO3C1, CuPhNEOsCl, ClgPhNE0¢C1 and ngPhNEO1C1 plots show wen defined 001 diffraction lines, and the d-spacing calculated from an average of the 001 reflections are listed in Table 3.2. CgPhNEOlCl and C7PhNE02C1 represent a transition from a small molecule packing pattern to the layered packing pattern. 123 intensity f r F CzoPhNEOyC1 C18PhNEOsC1 C14PhNEOSC1 A A A .__‘ ‘__ CwPhNEOaC1 C7PhN E0201 CaPhNEO1C1 CzPhNEOoC1 AA A.__ __. A ._~_ C1PhNEOoC1 A AA __ J 1 l 1 l n l 1 0 20 30 40 2 0 Figure 3.11. Powder XRD of the CxPhNEOyC, series of compounds. 124 Table 3.2. Average d-spacing for the CxPhNEoycl series of compounds calculated from powder XRD. compound average d-spacing (A) CloPhNEO3C1 32.7 CMPhNEOsCl 43.8 CuPhNCzEOsCl 44.2 ClsPhNE06C1 52.2 CzoPhNEO-lCl 58.2 CzoPhNCzEO-ICl 55 .4 CmPNACm 16.5 3) Spectroscopic characterization The IR spectra were measured on samples that were treated identically to the XRD samples. Figure 3.12 shows the 600 cm'l to 1600 cm'I region from the spectra. Most of the 1200 cm'l to 1400 cm" region is dominated by N=O stretching vibrations.“ 65 Peaks at 1468 cm'1 and 721.5 cm" indicate an ordered array of planar zigzag alkyl chains.66 Vibrations characteristic of helical CIEOy (1146 cm", 1115 cm'1 and 853 cm")67 did not show up until CzoPhNEO7C1. The spectral features of the CIEOy chains can easily be explained by the single crystal data for C7PhNE02C1. As can be seen from the torsional angles of the GED; listed in Table 3.3, the angles deviate from a perfect 72 helix. However E0 units far from the p-nitroaniline core, tend to assemble in the preferred 72 helix. The torsional angles of the alkyl chain are close to those of the ideal 125 CgoPhNEO7C1 l C18PhNE050, C14PhNE0501 absorbance CmPhNEOaC1 07thsozc1 A 1 l 1 l 1 l 1 l 1 600 800 1 000 1 200 1400 1 600 wavenumbers (cm") Figure 3.12. Mid-IR spectra of CxPhNEoyCl. The arrows identify the 853, 1115 and 1146 cm’1 vibrations characteristic of ethylene oxide chains with a helical conformation. 126 CzoPhNEOfi, C18PhNEOBC1 C14PhNEOSC1 CmPhNEOaC1 CythEOZC1 absorbance CaPhNEO1C1 C2PhNEOoC1 C1PhNEOoC1 1 l J l 1 l 3000 3200 3400 3600 wavenumber (cm") Figure 3.13. IR spectra of the N-H stretching region for CxPhNEOyCI. 127 Table 3.3. Torsional angles of the side chains in C7PhNEOz. Torsion angle position 1 XRD data (°) * Ideal data (°) " 03 C14 C15 04 63.9 65 C14 C1504 C16 172.7 188 Ethylene oxide C15 04 C16 C17 -177.4 -188 O4Cl6 C17 05 91.8 65 C16 C17 05 C18 170.0 188 C5 C7 C8 C9 -175.0 -180 C7 C8 C9 C10 177.0 180 Alkyl chain C8 C9 C10 C11 -l79.4 -180 C9 C10 C11 C12 178.9 180 C10 C11 C12 C13 -179.3 -180 Note: # Atom numbers are according to Figure 3.10. * Angles are derived from single crystal XRD data. A Ideal data based on polyethylene and polyethylene oxide crystal data. 128 planar zigzag conformation. The further the chains are from the p-nitroaniline core, the closer the angles are to the ideal value. Spectra of the N-H stretching region (3000 to 3700 cm") are plotted out in Figure 3.13. Since the peak position is sensitive to the environment of the amino groups,68 shifts in the peak positions indicate changes in hydrogen bonding, and hence the packing pattern of the materials. The spectra of CgPhNEOICl and CthNEOzCl differ from the other spectra, consistent with the powder XRD results. 4) Thermal behavior The thermal behavior of CxPhNEoycl was characterized by Differential Scanning Calorimetry (DSC). The operational procedures are the same as described in CHAPTER 2, except that the DSC run was extended to 150 °C for compounds having higher melting transitions. The second heating scans of CxPhNEoyCl are plotted in Figure 3.14. The scans are normalized with respect to sample weight and the temperature range displayed is limited to the region where thermal transitions were observed. All compounds show a single melting transition during heating. The low temperature exothermic transitions in the scans of C3PhNE01C1 and CmPhNEO3C1 are due to crystallization of super-cooled melt samples. Table 3.4 summarizes the melting points and heats of fusion for each compound. Figure 3.15 shows the relationship between the melting points and the length of the alkyl chain. For comparison, the data for p- nitroaniline and annealed samples of CxPhEoyCl are also shown. The data show a systematic trend. The melting points of the annealed samples of CxPhEOyCl increase with increases in the length of C" and CIEOy chain and start to level off at C13PhE06C1. The melting point of ClPhNEOoCl is close to that of p-nitroaniline, and the melting 129 endo therm --—-* CzoPhNEO7C1 Jl_ 1 J1 CmPhNEOaC1 W CyPhNEOzC1 CaPhNEO1C1 CzPhNEOoC1 J L C1PhNEOoC1 -30 10 50 90 130 temperature (C) Figure 3.14. DSC melting transitions of CxPhNEOyC 1. 130 180 C) 140 - o S3 31100 - o :5 I 8 l 2’ E 60 " A A l A ‘D o 2 o o 20 ~ 0 _2O 1 1 1 1 o 5 1o 15 20 No. of Carbons in the Alkyl Chains Figure 3.15. Melting points of C,PhNEO,C1 versus numbers of carbon atoms in the ethylene chain. (0) melting point of p-nitroaniline; (O) melting points of annealed CxPhEoyCl; (O) paired structures, (I) transitional structures and (A) lamellar structures of CxPhNEchl. 131 Table 3.4. Melting points and heats of fusion of the CxPhNEOy series of compounds.* compound melting points (°C) heat of fusion (J/g) p-nitroaniline 148.5 1 18 ClPhNEOo 132.4 1 19 CzPhNEOo 100.6 104 CsPhNEOI 89.6 110 CyPhNEOz 75. 1 106 CmPhNE03 54.3 1 l3 C14PhNE05 54.8 118 CmPhNan 57 .4 92 CzoPhNEoy 56.7 72 * Data derived from DSC measurements using the protocol described in CHAPTER 2. points decline with increases in the length of the side chains. CxPhEOyCl compounds with well-defined layered structures have melting points that are nearly independent of chain length and approach that of long chain CxPhEoyCl. The DSC data also show that none of the compounds show significant annealing effects or signs of stepwise melting and crystallization as was seen for the CxPhEoyC; compounds. When the side chains are sufficiently long, the molecules apparently adopt a common solid state structure. 132 3.3 Discussion 1 Transformation from paired structures to lamellar structures The antiparallel alignment of molecules is commonly seen in the solid state structures of molecules with large dipole moments. The pairing of strong dipoles lowers the overall potential energy, unless steric effects prevents efficient packing. The preference for pairing of dipoles is a major obstacle to the fabrication of noncentrosymmetric arrays of NLO chromophores.”26 Pairing cancels most, if not all of the dipole moments, makes electric field poling less efficient, and contributes to the relaxation of aligned polymer films.36 The chemical modification of chromophores to frustrate the formation of the paired structure is particularly important. The crystal structures of p-nitroaniline, ClPhNEOoC1 and CzPhNEOocl all have a paired subunit structure in their unit cells as shown in Figure 3.16. The angle of the dipole moments of the p-nitroaniline molecules in the paired structure is 180° and thus they perfectly cancel each other.”59 In CxPhNEoyCl the dipole moment of the molecule is aligned 1.5° (HyperChem calculation) toward the oxymethyl group along the axis defined by the nitro and amino groups (2 and 5 position) due to the introduction of oxygen ortho to amino group. The dipole moments fall between the amine and the oxygen. In the paired subunit of ClPhNEOoCl, the angle is 120°, and thus the net dipole moment of the subunit is half of the sum of the individual dipole moments. In the paired subunit of CzPhNEOoCl the dipole angle is 90°, so the net dipole moment in the subunit increases to three quarters. Increasing the side chain length to C7PhNE02C1 completely destroys the paired structure. The XRD scan shows that although CyPhNEOzCl no longer adopts the paired structure, its structure not a well-defined layered system and it 133 CzPhNEOoCl Figure 3.16. The p-nitroaniline subunit showing the relative alignment of the dipole moments in the paired structures. 134 represents the transition towards layer packing. The 001 d-spacin g feature is first seen in the XRD plot for CmPhNEO3C1, and the d-spacing increases with increases of the side chain length. The side chains prefer a fully interdigitated structure since the middle p- nitroaniline has a larger cross sectional area than benzene, creating space that enables interdigitation. The low angle XRD data for C14PhNE05C1, ClgPhNE06C1 and CzoPhNE07C1 and annealed samples of their structural analogs C14PhE05C1, ClgPhNE06C1 and CzoPhEO-lCl, are plotted in Figures 3.17-19. In all cases, the d-spacings of the C,PhNEO,C1 compounds are 6 A longer than the corresponding CxPhEoycl. Both sets of compounds have interdigitated side chains, but the addition of the nitro and amino groups to the aromatic ring limit the degree that the side chains can penetrate. The phase-separated structure induced by the amphiphilic side chains prevents the dipole moments from pairing. Figure 3.20 A is a schematic drawing of the phase- separated materials. The ethylene oxide chains aggregate in one layer and the ethylene chains will aggregate in the adjacent layers. The phase separated structure leads to aligned p-nitroaniline cores at the interface, creating a dipole-aligned structure at each interface. Figure 3.20 B shows that in the absence of phase separation, adjacent dipole moments pair. Separation of the amphiphilic side chains into lamellar structures is energetically favored by the crystallization of the alkyl and ethylene oxide side chains. Thus, the energy difference between the phase separation of amphiphilic side chains and the pairing of dipole moments determines the final structure of the materials. 135 intensity l (l C14PhNEOSC1 i X10 C14PhE0501 29 Figure 3.17. Low angle powder XRD of C14PhNE05C1 and annealed C14PhE05C1. 136 intensity ’1 C13PhNEOBC1 ” X10 C18PhEOGC1 0 2 4 6 8 1O 2 6 Figure 3.18. Low angle powder XRD of ClgPhNE06C1 and annealed ClgPhEO6C1. 137 CzoPhNE07C1 3:" (I) C 3 W .E C PhEOC X10 20 7 1 0 2 4 6 8 10 26 Figure 3.19. Low angle powder XRD of CzoPhNEO-ICI and annealed CzoPhEoyCl. 138 ethylene oxide layer p-nitroaniline interface alkyl layer aligned dipole moments alkyl + ethylene oxide p-nitroaniline interface paired dipole moments Figure 3.20. Schematic drawing of the CxPhNEOyCl solid state structure. A) Phase separated structure with aligned p-nitroaniline cores. B) Paired p-nitroaniline core structure that would form if there is no phase separation of alkyl and ethylene oxide chains. 139 The competition between the electronic pairing and phase separation of side chain can be calculated with a simple Coulomb model as shown in Figure 3.21. Several simplifying assumptions are made: 1) Only two molecules, the paired subunit are involved in the system. 2) Only crystallization of the side chains and electronic dipole interactions are considered. 3) The distances between the molecules of the paired subunit are the same as in the solid state structure of p-nitroaniline and the dipole moment of p- nitroaniline is used in the calculation. 4) Since the C,PhEo,c, is highly crystalline, the phase separation energy is approximated as AHfus, the crystallization of the side chains. A charge separation model was constructed that treats the two dipole moments as four separate charges spaced using the coordinates of the p-nitroaniline unit cell.58'59 The overall potential energy of the four charges can be calculated according to the Equation 3.4. The energy difference, AE, between the antiparallel and aligned structure is considered the pairing energy (Equation 3.5). The calculation omits the electrostatic interactions between layers, since they are inversely proportional to the square of distance, and should be small for side-chains of reasonable length. The AH“,s used in the calculation was the value for annealed CzoPhEoyCl measured by DSC. The theoretical results show that the dipole pairing energy and side chain phase separation energy are of the same magnitude. CzoPhEO-yC. has a larger phase separation energy than the dipole moment pairing energy. The phase separation energy is larger than the dipole pairing energy only when the side chains are reasonably long. The theoretical calculation agrees well with our experimental results. 140 T Dipole moment Ea Aligned dipole moments T T AB . . Ep Paired dipole moments _. Dipole moment and structural dimension of p-nitroaniline. Charge separation model of the adjacent dipole-dipole interactions (11 C12$ — q: (129 5.6 A 1' 23 <14 ED (13 GB | ‘—q> l— 3. 5 A 1'12 Paired dipole 1:“.p Aligned dipole Ea The charge separation model of paired dipoles is constructed from the single crystal data for antiparallel p-nitroanline molecules. The aligned dipole model uses the same dimensions as the paired dipole model. Figure 3.21. The theoretical calculation of dipole-dipole interaction energies. 141 1'12 (11 Q2 [‘12 = 1‘34 = 3.5 A f14=f23=5.6 A 1‘14 T23 = = 6.6 A r24 r13 f13 I24 94 q3 1'34 The imagined charges can be calculated from the dipole moment of p-nitroanline. Aligned dipole model: ~q. = -q2 = q; = q4 = 9.05 x 102' C Antiparallel paired dipole model: -q. = q; = -q3 = q4 = 9.05 x 10'21 C The difference in energy AE, between antiparallel paired dipole moments, Ep, and of aligned dipole moments, 13,, can be calculated from the Coulomb Energy Equation: E = 1/41teo x (qlqzlrlz + q1q3/r13 + qlq4/rl4 + q2q3/r23 + q2q4/r24 + q3q4/r34) Equation 3.4 E, = -1.03 x 10411; E, = -l.5x10’20 J The energy difference between paired and aligned structure: AE = Ea - Ep Equation 3.5 AB = 8.8x 104° J/2 molecules = 26 kJ/mol The phase separation energy of annealed CzoPhEO-yCl molecules: AHp = AHfu,* == 124 J/g = 86 kJ/mol AHp > AB * From DSC measurements of CzoPhEO-yCl. Continue of Figure 3.21 142 2 Paired structure of CmPNACm The importance of using amphiphilic side chains to drive phase separation is further demonstrated by the solid state properties of a p-nitroaniline derivative with uniform side chains at para positions. Compound CloPNACm was synthesized to study the influence that uniform side chains have on the structure of the material. Ten-carbon chains were used since C,PhNEO,C1 forms lamellar structures only when x 2 10 and y _>_ 3. Although single crystal XRD would make the structural study straightforward, a good quality crystal could not be obtained due to the long side chains. Thus, the structure of CloPNACm was deduced from powder XRD and IR data, combined with the known structure of p-nitroaniline. Figure 3.5 shows the single crystal structure of p-nitroaniline. Within each layer, the molecules are arranged head to tail to maximize the H-bonding interaction between the amino and nitro groups.“59 The spectra of CmPNACm and p-nitroaniline in the N-I-I stretching region (Figure 3.22) are almost identical. Since the amino and nitro groups are the only possible H-bonding interactions in CwPNAClo, the molecules must adopt the same head to tail structure during crystallization as shown in Figure 3.23. H-bonding aligns the p—nitroaniline cores and tilts the alkyl chains 60° relative to the H-bonding axis. The side chains interdigitate to fill the space created by H-bonding of the p-nitroaniline cores. A Hyper-Chem calculation for this geometry gave a d-spacing of 16.3 A, which agrees well with the experimental d-spacing of 16.5 A from powder XRD. The dipole moments of head to tail chains of nitroanilines are cancelled by a similar chain just above and aligned opposite to the first chain. The close relationship between the crystal 143 absorbance p -nitroaniline 3000 3200 3400 3600 wavenumber (cm") Figure 3.22. IR spectra of CmPNACm and p-nitroaniline in the N -H stretching region. 144 d-spacing 16.3 A side view of H-bonding network Top view showing the antiparallel arrangement of the dipoles. Figure 3.23. Proposed solid state structure of CloPNACm. 145 d-spacing 16.5 A C10PNAC10 C PNAC X 10 g 10 10 (n C 9 J LIN W .E p-nitroaniline 2 8 14 20 26 32 26 Figure 3.24. Powder XRD of CmPNACw and p-nitroaniline. The intensity of the middle scan was increased by 10, and scattering due to the alkyl chains was truncated for clarity. 146 structures of CloPNACm and p-nitroaniline is indicated by the similarity of powder XRD pattern of the two compounds (Figure 3.24). The paired structure of CmPNACm proves that uniform side chains lead to an antiparallel arrangement of dipole moments that minimizes the potential energy of the solid state structure. Antiparallel packing is a more effective way to cancel the dipole moment than the head to head arrangement, especially when the chromophores are in different layers separated by the long side chains. The amphiphilic side chains in CxPhNEoyCl are crucial for breaking down the antiparallel structure of dipole moment and aligning them in the interface. 3 H-bonding in the crystal structure of CxPhNEOyCl As in the case of p-nitroaniline and CmPNACm, H-bonding plays an important role in determining the structure of CxPhNEoyCl. Complications arise from more H- bonding sites being introduced into the system. In the CxPhNEoyCl system, the amino group is the only H-bond donor and three different acceptors are present, the ether oxygen of the ethylene oxide chains, the phenolic oxygen, and oxygens of the nitro group. Oxygens on the nitro group are .91)2 hybridized whereas the ether and phenolic oxygens are sp3 hybridized. The lone pairs of electrons on the phenolic oxygen participate in the 1t conjugation system of the benzene ring. Ranking the types of oxygen atoms in term of their accessibility for H-bonding gives the ether oxygen > phenolic oxygen > nitro oxygen. This ranking is solely determined by the electronic factors of the acceptor groups. The structural arrangement of the molecule must be taken into consideration when determining the actual H-bonding site. 147 Compounds C,PhNEO,C1 with relatively long side chains have layered structures with the p-nitroaniline cores aligned at the interface of the two side chains. This structural feature prevents the amino group from H-bonding with the ether oxygens of the ethylene oxide chains, and leaves open the possibility of the amino hydrogen and the nitro oxygen forming an H-bond at the same interface. The single crystal structures of compounds like ClPhNEOoCl show H-boning with intermolecular H-bonding between amino hydrogen and nitro oxygen as shown in Figure 3.25. One amino hydrogen participates in intermolecular H-bonding with a nitro group to give a zigzag structure. The H-bonding distances between the nitro oxygen and amino hydrogen are 2.11 A and 2.15 A. There also is an intramolecular H-bond between the phenolic oxygen and another amino hydrogen. The methyl group on the oxygen is oriented away from the H-bonding site. The intermolecular H-bonding distances are 2.53 A and 3.14 A, while a Hyper- Chem calculation shows a distance of 2.5 A for the CxPhNEO,C1 series. The p-nitroaniline group has two contradictory effects in the crystallization CxPhNEoyCl. H-bonding between the amino hydrogens and nitro oxygens facilitates the crystallization of the p-nitroaniline units, but for steric reasons inhibits side chain crystallization. At short side chain lengths, H—bonding is a major contribution to the heat of fusion of these materials, but for increasing side chain lengths, the relative importance of H-bonding becomes less important. For moderate length side-chains, the steric effect of the amino and nitro groups overwhelms the H-bonding contribution and thus accounts for the decrease of heat of fusion of C13PhNEO§C1 and CzoPhNEOyCl relative to the shorter chain compounds. 148 Figure 3.25. H-bonding arrangements in ClPhNEOoCl. Dashed lines indicate the H- bonding sites. Intermolecular H-bondings: A) 2.15 A, B) 2.11 A. Intramolecular H-bonding: C) 3.14 A, D) 2.53 A. 149 intermolecular H-bonding H-bonding acceptor —> H-bonding donor Intramolecular H-bonding Figure 3.26. I-l-bonding interactions in CzoPhNEO7C1. 150 Although the intermolecular H-bonding arrangement of ClPhNEOoCl cannot be realized for aligned structures with large CIEOy and C, chains, pseudo head-to-tail H- bonding between adjacent chromophores (Figure 3.26) is quite possible. The IR spectra (Figure 3.12) of C,PhNEO,C1 show the similarity of the N-H stretching vibrations and thus the H-bonding structures within the series. Intermolecular H-bonding can align the p-nitroaniline units and create an ordered structure, but capping the amino groups with methyl groups eliminates the H-bonding interaction and destabilizes the crystal structure. Figure 3.27 shows the wide angle powder XRD of CzoPhNEO7C1 and methyl capped CzoPhNCzEO-lCl. No features characteristic of the crystalline p-nitroaniline group is observed for CzoPhNCzEO-ICI, but the low angle XRD (Figure 3.28) shows that the two compounds have almost identical d-spacings. This further proves that the amino hydrogen is H-bonded to the nitro oxygen and not to the oxygens of the ethylene oxide chains. The XRD scans of CuPhNCzEOsCl and C14PhNE05C1 gave similar results (Figure 3.29). Although the methyl groups eliminate the H-bonding effects, it also increases steric hindrance and destabilizes side chain crystallization. The DSC scans in Figure 3.30 clearly show the influence of the p-nitroaniline core and methylated p- nitroaniline segments on the thermal behavior of CzoPhEO7C1. CzoPhNEO7C1 has a higher melting point than CzoPhEO-yCl due to H-bonding, but a lower heat of fusion because of the steric effects of the p-nitroaniline group. Elimination of H-bonding by converting the amine to its dimethyl derivative lowers melting point to that of CzoPhEO-ICI. The heat of fusion of CzoPhNC2EO7C1 is substantially lower than that of CzoPhEO-ICI due to the steric effects caused by the substitution of the benzene ring. 151 CzoPhNCZEO7C1 A A ‘ AA _ "7' —v w.— intensity 1 l l 1 02013116115070, Figure 3.27. Wide angle powder XRD of CzoPhNEO-ICI and CzoPhNCzEO-yCl. 152 CzoPhNC2E07C1 .E‘ (I) C 9 .S CzoPhNEOyC1 0 2 4 6 8 1 O 26 Figure 3.28. Low angle powder XRD of CzoPhNEO-1C1 and CzoPhNMeEOyCl. 153 intensity X5 26 Figure 3.29. Powder XRD of CuPhNEOsCl and C14PhNMeEOsC1. 154 C14PhN02EOSC1 C14PhNEOSC1 O 5 10 15 20 25 3O CzoPhNCZEO7C1 ’__ -—> CzoPhNEOyC1 _7 heat flow, endo 1 CzoPhEOyC1 1 l 1 l 1 l 30 4O 50 60 7O temperature (°C) Figure 3.30. DSC heating scans of CzoPhNMeEO-yCl, CzoPhNEOyCl and an annealed sample of CzoPhEO-ICl. 155 3.4 Conclusions Molecules with large dipole moments prefer to crystallize in antiparallel structures due to electrostatic interactions. This paired structure can be interrupted by chemical modification of the chromophore. The phase separation of amphiphilic diblock oligomers break the paired structure and allow alignment of the dipole moments at the interface of the side chains. A simple calculation shows that electronic pairing energy is smaller than the energies associated with phase separation and crystallization of diblock copolymers. H-bonding between the amino hydrogen and nitro oxygen is an important factor in the crystallization of these compounds. Since the phase separated structure locks the p- nitroaniline groups at the interface of the compounds, the only available H-bonding arrangements are the intramolecular H-bonding with a phenolic oxygen and intermolecular H-bonding with an oxygen of the nitro group. The latter facilitates crystallization at the interface. 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The reported melting points and boiling points are uncorrected. 1H and 13C NMR analyses were carried out at room temperature in CDC13 on a Varian Gemini-300 spectrometer. The chemical shifts were calibrated using solvent peaks from residual CHC13 and are reported relative to tetramethylsilane. Infrared spectra (IR) were measured in transmission mode on a Nicolet IR/42 FT-IR spectrometer under nitrogen. The samples were prepared by melting on a NaCl disc. The spectrum for each pure sample was obtained by subtracting the NaCl spectrum from that of the sample plus substrate. An Omega temperature control apparatus was used for IR spectrum taken above room temperature. Raman spectra were obtained at room temperature with a HoloProbe Raman Spectrograph excited at 633 nm. High resolution mass spectra were measured in the Mass Spectrometry Lab at University of South Carolina. All samples were purified by column chromatography and dried under vacuum at 60 °C for 4 days. DSC analyses of compounds were performed at heating rate of 10 °C/min in aluminum pans under a helium atmosphere on a Perkin Elmer DSC 7 instrument. The temperature was calibrated using indium and hexyl bromide standards, and liquid nitrogen was used as coolant. Most samples were melted and held at 100 °C for 5 min to 162 erase the thermal history. After quenching to —100 °C at a rate of 200 °C/min, samples were heated to 100 °C at a rate of 10 °C/min, cooled to —100 °C at a rate of 10 °C/min and heated to 100 °C at a rate of 10 °C/min. The DSC melting point was taken as the onset of the peak of the melting endotherm. DSC samples were annealed by holding at the desired temperature for 2 hours in the sample pan. Heats of fusion were calculated from the edothermic peak using the accompanied functions of the DSC 7 software. XRD patterns were recorded on a Rigaku rotaflex 2003 diffractometer equipped with a rotating anode, Cu Ka x-ray radiation (8 = 1.541838a) and a curved crystal graphite monochromator. The x-ray instrument was operated at 45 kV and 100 mA. Data were collected at 0.05 degree intervals between 05° and 45° at a scanning rate of 2°/min. The samples were prepared by grinding the sample into a powder and spreading the solid samples on the window of the glass sample holder with a spatula. 4.2 Compound identification numbers (ID) Most of the compounds synthesized in this project are series of compounds, which have similar structures but different side chain lengths. Their generic structures are shown in synthetic Schemes 2.3, 2.4, 3.2, 3.3 and 3.4. For indexing purposes, each compound is assigned a compound ID beginning with a number for the generic structure, which corresponds to that used in the synthetic schemes. A lower case letter following the number is used to differentiate molecules with same generic structure, but with different side chain lengths. The compound IDs are summarized in Tables 4.1-4.9. 163 Table 4.1. Compound IDs for 1 (Scheme 2.3). a = 2 a = 3 a : 4 1a 1b 1c Table 4.2. Compound IDs for 2 (Scheme 2.3). a = 2 a = 3 a = 4 2a 2b 2c Table 4.3. Compound IDs for 3 (Scheme 2.3). y=4 y=5 y=6 y=7 3a 3b 3c 3d Table 4.4. Compound IDs for 4 (Scheme 2.3). y=4 y=5 y=6 y=7 4a 4b 4c 4d Table 4.5. Compound IDs for 5 (Scheme 2.4). y:4 y=5 y=6 y=7 5a 5b 5c 5d Table 4.6. Compound IDs for 6 (Scheme 2.4). x=l4 x=l6 x=18 x=20 6a 6b 6c 6d 164 Table 4.7. Compound ID for 7 (Scheme 2.4). x=l4 x=l6 x=18 x=20 7 7a 7b 7c 7d Table 4.8. Compound IDs for 8 (CxPhEOyCl) (Scheme 2.4). 8w y=1 y=2 y=3 y=4 y=5 y=6 y=7 X = 14 814,1 814,2 814,3 314,4 314,5 314,6 314,7 X = 16 816,1 816,2 316,3 816,4 816,5 316,6 316,7 X = 13 318,1 818,2 318,3 818,4 318,5 313,6 318,7 X = 20 320,1 820,2 320,3 320,4 320,5 320,6 320,7 Table 4.9. Compound IDs for 9-15 (Scheme 3.2 & 3.3). a b c d e f g h x=1 x-2 x=3 x=7 x=10 x=14 x=18 x=20 y=0 y=0 y=l y=2 y=3 y=5 y=6 y=7 9 9a 9b 9c 9d 9e 9f 9g 9h 10 10a 10b 10c 10d 108 101' 10g 101] 11 11a 11b 11c 11d lle 11f 11g 11h 12 128 121) 12c 12d 128 12f 12g 12h 13 13a 13b 13c 13d 13¢ 13f 13g 13h 14 14a 14b 14c 14d 14e 14f 14g 141] 15 15e 15f 15h 165 4.3 Material synthesis 1 Synthesis of monotosylated polyethylene glycols l-Tosyloxy-3-oxapentan-5-ol [Ts(OCH2CH2)2OH] (1a) Diethylene glycol (100 mL, 0.84 mol) was dissolved in THF (50 mL) and cooled to 0 °C in an ice bath. A solution of KOH (23 g, 0.41 mol) in 40 mL water was slowly added to the mixture, and then a solution of TsCl (40 g, 0.21 mol) in 150 mL THF was added drop-wise over one hour with vigorous stirring. After stirring overnight in an ice bath, the mixture was poured into distilled water (500 mL) and extracted with CHzClz (2 X 250 mL). The combined organic solutions were washed with saturated NaHC03 solution (2 x 200 mL), distilled water (2 x 200 mL), dried over MgSO4, and concentrated under reduced pressure. The crude oil was dissolved in methanol (300 mL), and stored in a freezer over night. The ditosylate byproduct crystallized and was removed by filtration. The filtrate was concentrated under reduced pressure to give 41.6 g (76%) of Ts(OCH2CH2)2OH as a colorless oil‘. 1H NMR (300 MHz, CDC13) 5 1.92 (s, 1H), 2.41 (s, 3H), 3.50 (t, 2H), 3.65 (m, 4H), 4.18 (t, 2H), 7.35 (d, 2H), 7.78 (d, 2H). 1-Tosyloxy-3,6-dioxaoctan-8-ol [Ts(OCH2CH2)3OH] (1b) Obtained as described above as a clear colorless oil1 in 89% yield. 1H NMR (300 MHz, CDC13) 8 1.92 (s, 1H), 2.41 (s, 3H), 3.50 -3.65 (m, 10H), 4.18 (t, 2H), 7.35 (d, 2H), 7.78 (d, 2H). l-Tosyloxy-3,6,9-trioxaundecan-ll-ol [Ts(OCH2CH2)4OH] (1c) Obtained as described above as a clear colorless oil2 in 92% yield. 1H NMR (300 MHz, CDC13) 8 1.92 (s, 1H), 2.41 (s, 3H), 3.50 -3.65 (m, 14H), 4.18 (t, 2H), 7.35 (d, 2H), 7.78 (d, 2H). 166 2 THP protection of monotosylated polyethylene glycols 2-(1-Tosyloxy-3-oxapentan-5-oxy)tetrahydropyran [Ts(OCH2CH2)2OTHP] (2a) Over a period of 5 minutes, dihydro-4H-pyran (50 g, 0.59 mol) was added drop-wise to a stirred solution of 1a (48 g, 0.18 mol) and p-toluenesulfonic acid monohydrate (2.50 g, 13.1 mmol) in anhydrous dioxane (500 mL) at 20 °C. After stirring for 15 minutes, half—saturated methanolic ammonia was added until the solution was slightly basic. The mixture was concentrated under reduced pressure, and redissolved in CHC13 (300 mL). The solution was washed with 5% NaCl (3 x 200 mL), dried over MgSO4, and concentrated under reduced pressure to give 61.4 g (97%) of Ts(OCH2CH2)zOTHP as a clear light yellow 0113. The product was used in the next step without further purification. 1H NMR (300 MHz, CDC13) 5 1.40-1.90 (m, 6H), 2.41 (s, 3H), 3.40-3.80 (m, 8H), 4.18 (t, 3H), 4.60 (t, 1H), 7.35 (d, 2H), 7.78 (d, 2H). 2-(1-Tosyloxy-3,6-dioxaoctan-8-oxy)tetrahydropyran [Ts(OCH2CH2)3OTHP] (2b) Obtained as described above as a clear light yellow oil4 in 98% yield. 1H NMR (300 MHz, CDC13) 6 1.40-1.90 (m, 6H), 2.41 (s, 3H), 3.40-3.80 (m, 12H), 4.18 (t, 3H), 4.60 (t, 1H), 7.35 (d, 2H), 7.78 (d, 2H). 2-(1-Tosyloxy-3,6,9-trioxaundecan-1l-oxy)tetrahydropyran [Ts(OCHzCH2)4OTHP] (2c) Obtained as described above as a clear light yellow oil5 in 98% yield. 1H NMR (300 MHz, CDC13) 5 1.40-1.90 (m, 6H), 2.41 (s, 3H), 3.40-3.80 (m, 16H), 4.18 (t, 3H), 4.60 (t, 1H), 7.35 (d, 2H), 7.78 (d, 2H). 167 3 THP protection of polyethylene glycol monomethyl ethers 2-(2,5,8,11,14-pentaoxahexadecan-16-oxy)tetrahydropyran [CH3(OCH2CH2)5OTHP] (3b) Over a period of 20 minutes, a solution of triethylene glycol monomethyl ether (29 mL, 0.18 mol) in THF (200 mL) was added drop-wise to a mixture of sodium hydride (9.0 g, 0.38 mol) in THF (150 mL) at reflux. Heating was continued for an hour, and then a solution of 2-(5-tosyloxy-3- oxapentanoxy)tetrahydropyran (61.4 g, 0.178 mol) in THF (200 mL) was added to the mixture. After stirring overnight, the precipitates were removed by filtration and the THF solution was concentrated under reduced pressure to give 53.8 g, (89%) of CH3(OCH2CH2)5OTHP as a clear light yellow oi16. The product was used in the next step without further purification. 1H NMR (300 MHz, CDC13)8 l.40-1.90 (m, 6H), 3.36 (s, 3H), 3.50-3.80 (m, 22H), 4.60 (t, 3H). 2-(2,5,8,ll-hexaoxanonadecan-13-oxy)tetrahydropyran [CH3(OCH2CH2)4OTHP] (38) Obtained as described above as a clear light yellow oil in 80% yield. 1H NMR (300 MHz, CDC13) 5 1.40-1.90 (m, 6H), 3.36 (s, 3H), 3.50-3.80 (m, 18H), 4.60 (t, 3H). 2- (2,5,8, 1 1,14,17-hexaoxanonadecan- 19-oxy)tetrahydropyran [CH3(OCH2CH2)5OT HP] (3c) Obtained as described above as a clear light yellow oil in 78% yield. 1H NMR (300 MHz, CDC13) 8 1.40-l.90 (m, 6H), 3.36 (s, 3H), 3.50-3.80 (m, 26H), 4.60 (t, 3H). 2-(2,5,8,1 l ,14,17,20-heptaoxadocosan-22-oxy)tetrahydropyran [CH3(OCH2CH2)7OTHP] (3d) Obtained as described above as a clear light yellow oil in 168 82% yield. 1H NMR (300 MHz, CDC13) 5 1.40-1.90 (m, 6H), 3.36 (s, 3H), 3.50-3.80 (m, 30H), 4.60 (t, 3H). 4 Deprotection of polyethylene glycol monomethyl ethers 2,5,8,11,14-pentaoxahexadecan-16-01 [CH3(OCH2CH2)50H] (4b) HCI (50 mL, 2M) was added to an ethanol solution (400 mL) of 2-(14-methoxy-3,6,9,12- tetraoxatetradecan-1-oxy)tetrahydropyran (50.0 g, 0.147 mol) and the mixture was refluxed for 5 hours. Concentration under reduced pressure and vacuum distillation gave a 72% yield of CH3(OCH2CH2)50H. bp 102 °C (40 mTorr) (lit.7 bp 145 — 147 °C/1 Torr). 1H NMR (300 MHz, CDC13) 6 2.33 (s, 1H), 3.36 (s, 3H), 3.50-3.80 (m, 20H). 2,5,8,ll-hexaoxanonadecan-l3-ol [CH3(OCH2CH2)4OH] (4a) Obtained as described above as a clear colorless oil in 72% yield after vacuum distillation. bp 100 °C (40 mTorr) (111.7 bp 160 — 167 °c (1 Torr)). 'H NMR (300 MHz, CDC13) 5 2.33 (s, 1H), 3.36 (s, 3H), 3.50-3.80 (m, 24H). 2,5,8,11,14,17-hexaoxanonadecan-l9-ol [CH3(OCH2CH2)GOH] (4c) Obtained as described above as a clear colorless 0117in 61% yield after vacuum distillation. bp 135 °C (40 mTorr) (lit.7 bp 160 — 167 °C (1 Torr)). 1H NMR (300 MHz, CDC13) 5 2.33 (s, 1H), 3.36 (s, 3H), 3.50-3.80 (m, 24H). 2,5,8,11,14,17,20-hexaoxadocosan-22-ol [CH3(OCH2CH2)7OH] (4d) Obtained as described above as a clear colorless oil in 45% yield after vacuum distillation. bp 205 °C (40 mTorr) (lit.8 bp 198 —— 205 °C (0.04 Torr)). 1H NMR (300 MHz, CDC13) 5 2.33 (s, 1H), 3.36 (s, 3H), 3.50-3.80 (m, 28H). 169 5 Synthesis of tosylated derivates of polyethylene glycol monomethyl ethers 4-Tosyloxy-2-oxabutane [TsOCHzCHzOCH3] (5a) Prepared according to the procedure for 5-tosyloxy-3-oxapentanol except that stoichiometric amounts of starting materials were used. Yield: 98% as a clear colorless oil. 1H NMR (300 MHz, CDC13) 8 2.43 (s, 3H), 3.29 (s, 3H), 3.56 (t, 2H), 4.15 (t, 2H), 7.31 (d, 2H), 7.77 (d, 2H). 7-Tosyloxy-2,5-dioxaheptane [Ts(OCH2CH2)2OCH3] (5b) Obtained as described above as a clear colorless oil in 99% yield. 1H NMR (300 MHz, CDCl3) 8 2.43 (s, 3H), 3.33 (s, 3H), 3.45 (t, 2H), 4.04 (t, 2H), 3.58 (t, 2H), 7.68 (d, 2H) 3.67 (t, 2H), 4.17 (t, 2H), 7.31 (d, 2H), 7.77 (d, 2H). lO-Tosyloxy-2,5,8-trioxadecane [Ts(OCH2CH2)3OCH3] (5c) Obtained as described above as a clear colorless oil9 in 99% yield. 1H NMR (300 MHz, CDC13) 8 2.3 (s, 3H), 3.22 (s, 3H), 3.28-3.70 (m, 10H), 4.04 (t, 2H), 7.24 (d, 2H), 7.68 (d, 2H). 13-Tosyloxy-2,5,8,1l-tetraoxatridecane [Ts(OCH2CH2)4OCH3] (5d) Obtained as described above as a clear colorless oil in 99% yield. 1H NMR (300 MHz, CDC13) 8 2.3 (s, 3H), 3.22 (s, 3H), 3.28-3.70 (m, 14H), 4.04 (t, 2H), 7.24 (d, 2H), 7.68 (d, 2H). l6-Tosyloxy-2,5,8,l1,14-pentaoxahexadecane [Ts(OCH2CH2)50CH3] (5e) Obtained as described above as a clear colorless oil10 in 99% yield. ‘H NMR (300 MHz, CDC13)8 2.3 (s, 3H), 3.22 (s, 3H), 3.28-3.70 (m, 18H), 4.04 (t, 2H), 7.24 (d, 2H), 7.68 (d, 2H). 19-Tosyloxy-2,5,8,11,14,17-hexaoxanonadecane [Ts(OCH2CH2)6OCH3] (51') Obtained as described above as a clear colorless oil11 in 99% yield. 1H NMR (300 MHz, CDC13) 8 2.3 (s, 3H), 3.22 (s, 3H), 3.28-3.70 (m, 24H), 4.04 (t, 2H), 7 .24 (d, 2H), 7.68 (d, 2H). 170 22-Tosyloxy-2,5,8,l1,14,17,19-heptaoxadocosane [Ts(OCH2CH2)70CH3] (5g) Obtained as described above as a clear colorless oil12 in 99% yield. 1H NMR (300 MHz, CDC13) 8 2.3 (s, 3H), 3.22 (s, 3H), 3.28-3.70 (m, 28H), 4.04 (t, 2H), 7.24 (d, 2H), 7.68 (d, 2H). 6 Coupling of alkyl chains to benzene ring 4-Deeylanisole [CH3(CH2)9PhOCH3] (6a) A solution of l—decylbromide (44.2 mL, 0.2 mol) in THF (200 mL) was added under nitrogen to Mg tumings (5.0 g, 0.22 mol) over a period of 15 minutes. Heating was applied to initiate the reaction. After the reaction was no longer exothermic, the mixture was refluxed for an additional hour. The Grignard solution was transferred while hot to a stirred THF solution (250 mL) of 4- chloroaniline (20 g, 0.14 mol) and (dppp)C12Ni (0.28 g, 7.0 mmol). The mixture was refluxed for 2 days under nitrogen and then cooled to room temperature. The mixture was washed with saturated aqueous NaCl (3 X 200 mL), dried over MgSO4 and concentrated under reduced pressure. The crude brown solid was purified by recrystallization from pentane and ether to give 25 g (72%) of CH3(CH2)9PhOCH3 as a white crystalline powder. mp 16.2 — 17.1 °C (lit.'3 mp 17.0 — 17.5 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 16H), 1.55 (t, 2H), 2.52 (t, 2H), 3.78 (s, 3H), 6.80 (d, 2H), 7.08 (d, 2H). 4-Tetradecylanisole [CH3(CH2)13PhOCH3] (6b) Obtained as described above as a white crystalline powder in 61% yield. mp 36.5 °C (lit.14 mp 38 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 24H), 1.55 (t, 2H), 2.52 (t, 2H), 3.78 (s, 3H), 6.80 (d, 2H), 7.08 (d, 2H). I‘IRMS calc. fOI' C21H3601 304.2766, found 304..2767 171 4-Hexadecylanisole [CH3(CH2)15PhOCH3] (6c) Obtained as described above as a white crystalline powder in 61% yield. mp 44.1 °C (lit.15 mp 43 — 44 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 28H), 1.55 (t, 2H), 2.52 (t, 2H), 3.78 (s, 3H), 6.80 (d, 2H), 7.08 (d, 2H). HRMS calc. for C23114001 332.3079, found 332.3086. 4-Octadecylanisole [CH3(CH2)17PhOCH3] (6d) Obtained as described above as a white crystalline powder13 in 45% yield. mp 51.5 °C (lit.16 mp 51 — 52 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 32H), 1.55 (t, 2H), 2.52 (t, 2H), 3.78 (s, 3H), 6.80 (d, 2H), 7.08 (d, 2H). HRMS calc. for CZSHMOl 360.3392, found 360.3393. 4-Eicosylanisole [CH3(CH2)19PhOCH3] (6e) Obtained as described above as a white crystalline powder in 45% yield. mp 58.1 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-l.32 (b, 36H), 1.55 (t, 2H), 2.52 (t, 2H), 3.78 (s, 3H), 6.80 (d, 2H), 7.08 (d, 2H). HRMS calc. for C27H430] 388.3705, found 388.3691. 7 Synthesis of 4-alkylphenols 4-Decylphenol [CH3(CH2)9PhOH] (7a) An anhydrous solution of 4-decy1anisole (7.50 g, 30.2 mmol) in methylene chloride (200 mL) was cooled in a dry ice/acetone bath. After the temperature reached equilibrium, a solution of BBr3 (2.9 mL, 30 mmol) in methylene chloride (50 mL) was added over a period of 10 minutes. The mixture was allowed to warm to room temperature and stirred over night. The reaction was quenched by the drop-wise addition of water (100 mL) and extracted with ether (200 mL). The organic layer was washed with saturated aqueous NaCl (200 mL), dried over MgSO4, and concentrated under reduced pressure. The crude white solid was recrystallized from cold methylene chloride to give 7.0 g (99%) of 4-decylphenol as white crystalline powder. mp 172 57.5 — 58.5 °C (lit.l3 mp 57.5 — 58.5 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 16H), 1.55 (t, 2H), 2.50 (t, 2H), 4.45 (s, 1H), 6.72 (d, 2H), 7.02 (d, 2H). 4-Tetradecylphenol [CH3(CH2)13PhOH] (7b) Obtained as described above as a white crystalline powder in 90% yield. mp 72.5 — 73.5 °C (lit.l7 mp 73 — 74 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 24H), 1.55 (t, 2H), 2.50 (t, 2H), 4.45 (s, 1H), 6.72 (d, 2H), 7.02 (d, 2H). 4-Hexadecylphenol [CH3(CH2)15PhOH] (7c) Obtained as described above as a white crystalline powder in 90% yield. mp 78 — 79 °C (lit.18 mp 78 - 79 °C). 1H NMR (300 MHz, CDCl3) 8 0.85 (t, 3H), l.l8-1.32 (b, 28H), 1.55 (t, 2H), 2.50 (t, 2H), 4.45 (s, 1H), 6.72 (d, 2H), 7.02 (d, 2H). 4-Octadecylphenol [CH3(CH2)17PhOH] (7d) Obtained as described above as a white crystalline powder in 91% yield. mp 82.0 — 84.0 °c (lit.'3 mp 83.0 — 84.0 °C). 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 32H), 1.55 (t, 2H), 2.50 (t, 2H), 4.45 (s, 1H), 6.72 (d, 2H), 7.02 (d, 2H). 4-Eicosylphenol [CH3(CH2)19PhOH] (7e) Obtained as described above as a white crystalline powder in 89% yield. mp 88.0 — 89.0 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 36H), 1.55 (t, 2H), 2.50 (t, 2H), 4.45 (s, 1H), 6.72 (d, 2H), 7.02 (d, 2H). HRMS calc. for C26H4601 374.3549, found 374.3539. 8 Synthesis of CxPhEOyCl 4-Decy1-1-(2,5,8-trioxadecan-10-oxy)benzene [CH3(OCH2CH2)3OPh(CH2)9CH3] (810,3) A THF solution (100 mL) of 7a (2.5 g, 11 mmol) was added drop-wise to a mixture of sodium hydride (0.50 g, 21 mmol) in anhydrous THF (50 mL) under nitrogen. After refluxing for an hour, a THF solution (100 173 mL) of SC (4.00 g, 12.6 mmol) was added and heating was continued overnight. The mixture was cooled to room temperature and filtered. The filtrate was washed with saturated aqueous NaCl (3 x 200 mL), dried over MgSO4, and concentrated under reduced pressure. The resulting oil was purified using flash chromatography (60/40 ethyl acetate/hexane) to yield 3.4 g (75%) of product as a colorless 011. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 14H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52- 3.75 (m, 8H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C23H4004 380.2927, found 380.2921. 4-Tetradecyl-1-(2-oxabutan-4-oxy)benzene[CH3OCH2CH20Ph(CH2)13CH3] (814,1) Obtained as described above as a white crystalline solid in 80% yield after purification by column chromatography (35/65 ethyl acetate/hexane). mp 30.1 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.73 (t, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C23H4002 348.3028, found 348.3021. 4-Tetradecyl-1-(2,5-dioxaheptan-7-oxy)henzene [CH3(OCH2CH2)2OPh(CH2)13CH3] (814,2) Obtained as described above as a white crystalline solid obtained in 77% yield after purification by column chromatography (40/60 ethyl acetate/hexane). mp 30.5 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.55 (t, 2H), 2.72 (d, 2H), 3.83 (t, 2H), 4.10 (t, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C25H4403 392.3290, found 392.3291. 4-Tetradecyl-1-(2,5,8-trioxadecan-lO-oxy)benzene [CH3(OCH2CH2)3OPh(CHz)13CH3] (814,3) Obtained as described above as a white solid 174 in 73% yield after purification by column chromatography (50/50 ethyl acetate/hexane). mp 16.1 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 8H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C27H4304 436.3553, found 436.3549. 4-Tetradecyl-1-(2,5,8,l l-tetraoxatridecan-13-oxy)benzene [CH3(OCH2CH2)4OPh(CH2)13CH3] (814,4) Obtained as described above as a white solid in 60% yield after purification by column chromatography (60/40 ethyl acetate/hexane). mp 22.3 °C. lH NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for ConszOs 480.3815, found 480.3806. 4-Tetradecyl-l-(2,5,8,11,l4-pentaoxahexadecan-16-oxy)benzene [CH3(OCH2CH2)50Ph(CH2)13CH3] (814,5) Obtained as described above as a white solid in 52% yield after purification by column chromatography (80/40 ethyl acetate/hexane). mp 31.7 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 161-I), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7 .04 (d, 2H). HRMS calc. for C31H5606 524.4077, found 524.4081. 4-TetradeeyI-l-(2,5,8,l1,14,17-hexaoxanonadecan-19-oxy)benzene [CH3(OCH2CH2)50Ph(CH2)13CH3] (814,6) Obtained as described above as a white solid in 65% yield after purification by column chromatography (80/20 ethyl acetate/hexane). mp 26.9 °C. 1H NMR (300 MHz, CDCl3) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C33H(,OO7 568.4339, found 568.4327. 175 4-Tetradecyl-l-(2,5,8,ll,14,17,19-heptaoxadocosan-22-oxy)benzene [CH3(OCHzCH2)7OPh(CH2)13CH3] (814,7) A white solid obtained in 62% yield after purification by column chromatography (80/20 ethyl acetate/hexane). mp 29.1 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18—1.32 (b, 22H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 24H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C35H6403 612.4601, found 612.4607. 4-Hexadecyl-1-(2-oxabutan-4-oxy)benzene [CH3OCH2CHzOPh(CH2)15CH3] (816,1) Obtained as described above as a white crystalline solid in 71% yield after purification by column chromatography (35/65 ethyl acetate/hexane). mp 38.3 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), l.l8-1.32 (b, 26H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.73 (t, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C25H4402 376.3341, found 376.3335. 4-Hexadecyl-1-(2,5-dioxaheptan-7-oxy)benzene [CH3(OCH2CH2)2OPh(CH2)15CH3] (816,2) Obtained as described above as a white crystalline solid in 79% yield after purification by column chromatography (40/60 ethyl acetate/hexane). mp 28.6 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 26H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.55 (t, 2H), 2.72 (d, 2H), 3.83 (t, 2H), 4.10 (t, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for Cal-14303 420.3603, found 420.3601. 4-Hexadecyl-1-(2,5,8-trioxadecan-lO-oxy)benzene [CH3(OCH2CH2)3OPh(CH2)15CH3] (815,3) Obtained as described above as a white solid in 78% yield after purification by column chromatography (50/50 ethyl acetate/hexane). mp 23.6 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 26H), 1.55 (t, 2H), 176 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 8H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C29H5204 464.3866, found 464.3857. 4-Hexadecyl-1-(2,S,8,1l-tetraoxatridecan-13-oxy)benzene [CH3(OCHzCH2)40Ph(CH2)15CH3] (816,4) Obtained as described above as a white solid in 51% yield after purification by column chromatography (60/40 ethyl acetate/hexane). mp 23.6 °C. 1H NMR (300 MHz, CDCl3) 8 0.85 (t, 3H), 1.18-1.32 (b, 26H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C31H5605 508.4128, found 508.4127. 4-Hexadecyl-1-(2,5,8,l1,14-pentaoxahexadecan-16-oxy)benzene [CH3(OCH2CH2)5OPh(CH2)15CH3] (815,5) Obtained as described above as a white solid in 71% yield after purification by column chromatography (70/30 ethyl acetate/hexane). mp 36.8 °C. 1H NMR (300 MHz, CDCl3) 8 0.85 (t, 3H), 1.18-1.32 (b, 26H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 16H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C33HboOb 552.4390, found 552.4370. 4-Hexadecyl-1-(2,5,8,l1,14,17-hexaoxanonadecan-19-oxy)benzene [CH3(OCH2CH2)6OPh(CH2)15CH3] (816,5) Obtained as described above as a white solid in 65% yield after purification by column chromatography (80/20 ethyl acetate/hexane). mp 232°C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), l.l8-1.32 (b, 26H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C35H6407 596.4652, found 596.4660. 4-Octadecyl-l-(2-oxabutan-4-oxy)benzene [CH3OCH2CH20Ph(CH2)11CH3] (813,1) Obtained as described above as a white crystalline solid in 72% yield after purification by column chromatography (35/65 ethyl acetate/hexane). mp 46.2 °C. 1H 177 NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-l.32 (b, 30H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.73 (t, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C27114302 404.3654, found 404.3656. 4-Octadecyl-1-(2,5-dioxaheptan-7-oxy)benzene [CH3(OCH2CH2)2OPh(CH2)17CH3] (813,2) Obtained as described above as a white crystalline solid in 81% yield after purification by column chromatography (40/60 ethyl acetate/hexane). mp 37.4 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 30H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.55 (t, 2H), 2.72 (d, 2H), 3.83 (t, 2H), 4.10 (t, 2H), 6.80 (d, 2H), 7 .04 (d, 2H). HRMS calc. for C29H5203 448.3916, found 448.3918. 4-Octadecyl-1-(2,5,8-trioxadecan-10-oxy)benzene [CH3(OCH2CH2)3OPh(CH2)17CH3] (813,3) Obtained as described above as a white solid in 71% yield after purification by column chromatography (50/50 ethyl acetate/hexane). mp 35.9 °C. lH NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 30H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 8H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C31H5604 492.4179, found 492.4189. 4-Octadecyl-1-(2,5,8,1l-tetraoxatridecan-13-oxy)benzene [CH3(OCH2CH2)4OPh(CH2)17CH3] (813,4) Obtained as described above as a white solid in 65 % yield after purification by column chromatography (60/40 ethyl acetate/hexane). mp 36.1 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 30H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C33116005 536.4441, found 536.4447. 4-Octadecyl-1-(2,5,8,l1,14-pentaoxahexadecan-16-oxy)benzene [CH3(OCH2CH2)50Ph(CH2)17CH3] (813,5) Obtained as described above as a white solid 178 in 74% yield after purification by column chromatography (70/30 ethyl acetate/hexane). mp 42.1 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 30H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 1610, 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C35H(,406 580.4703, found 580.4694. 4-Octadecyl-1-(2,5,8,l1,14,17-hexaoxanonadecan-19-oxy)benzene [CH3(OCH2CH2)6OPh(CH2)17CH3] (813,5) Obtained as described above as a white solid in 71% yield after purification by column chromatography (80/20 ethyl acetate/hexane). mp 36.9 °C. lH NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 30H), 1.55 (t, 2H), 2.52 (t, 210, 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C37H6307 624.4965, found 624.4975. 4-Octadecyl-1-(2,5,8,l1,14,17,19-heptaoxadocosan-22-oxy)benzene [CH3(OCHZCH2)7OPh(CH2)17CH3] (813,7) Obtained as described above as a white solid in 51% yield after purification by column chromatography (90/ 10 ethyl acetate/hexane). mp 38.3 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 30H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 24H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C39H7203 668.5227, found 668.5202. 4-Eicosyl-1-(2-oxabutan-4-oxy)benzene [CH3OCH2CH20Ph(CH2)19CH3] (820,1) Obtained as described above as a white crystalline solid in 78% yield after purification by column chromatography (35/65 ethyl acetate/hexane). mp 53.1 °C. lH NIVIR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 34H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.73 (t, 2H), 6.80 (d, 2H), 7 .04 (d, 2H). HRMS calc. for ConszOz 432.3967, found 432.3966. 179 4-Eicosyl-1-(2,5-dioxaheptan-7-oxy)benzene [CH3(OCH2CH2)2OPh(CH2)19CH3] (820,2) Obtained as described above as a white crystalline solid in 75% yield after purification by column chromatography (40/60 ethyl acetate/hexane). mp 44.5 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 22H), 1.55 (t, 2H), 2.51 (t, 2H), 3.43 (s, 3H), 3.55 (t, 2H), 2.72 (d, 2H), 3.83 (t, 2H), 4.10 (t, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C31H5603 476.4229, found 476.4232. 4-Eicosyl-l-(2,5,8-trioxadecan-10-oxy)benzene [CH3(OCHzCH2)3OPh(CH2)19CH3] (820,3) Obtained as described above as white solid in 82% yield after purification by column chromatography (50/50 ethyl acetate/hexane). mp 45.9 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 34H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 8H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C33116004 520.4492, found 520.4484. 4-Eicosyl-1-(2,5,8,1l-tetraoxatridecan-l3-oxy)benzene [CH3(OCH2CH2)4OPh(CH2)19CH3] (820,4) Obtained as described above as a white crystalline solid in 72% yield after purification by column chromatography (60/40 ethyl acetate/hexane). mp 45.4 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 34H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C35H6405 564.4754, found 564.4748. 4-Eicosyl-1-(2,5,8,11,14-pentaoxahexadecan-l6-oxy)benzene [CH3(OCH2CH2)50Ph(CH2)19CH3] (820,5) Obtained as described above as a white crystalline solid in 66% yield after purification by column chromatography (70/30 ethyl acetate/hexane). mp 45.0 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 180 34H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 16H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C37H6306 608.5016, found 608.5020. 4-Eicosyl-1-(2,5,8,ll,14,17-hexaoxanonadecan-19-oxy)benzene [CH3(OCH2CH2)6OPh(CH2)19CH3] (820,6) Obtained as described above as a white crystalline solid in 62% yield after purification by column chromatography (80/20 ethyl acetate/hexane). mp 44.3 °C. 1H NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 34H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 20H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C39H7zO7 652.5278, found 652.5298. 4-Eicosyl-l-(2,5,8,11,14,17,l9-heptaoxadocosan-22-oxy)benzene [CH3(OCH2CH2)7OPh(CH2)19CH3] (820,7) Obtained as described above as a white crystalline solid in 42% yield after purification by column chromatography (90/10 ethyl acetate/hexane). mp 43.6 °C. lH NMR (300 MHz, CDC13) 8 0.85 (t, 3H), 1.18-1.32 (b, 34H), 1.55 (t, 2H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.75 (m, 24H), 3.82 (t, 2H), 4.08 (s, 2H), 6.80 (d, 2H), 7.04 (d, 2H). HRMS calc. for C41H7603 696.5540, found 696.5538. 9 Nitration of alkylphenol 4-n-Decyl-2-nitrophenol [CH3(CH2)9PhN020H] (9e) Over a period of 5 minutes, 70% HNO; (0.83 g, 9.2 mmol) in 1.5 mL of glacial acetic acid at 0 °C was slowly added to a vigorously stirred solution of 7a (1.2 g, 5.1 mmol) in 5 mL of glacial acetic acid at 15 °C. A precipitate was formed after a few minutes. The mixture was allowed to warm to room temperature over a period of 15 min. The reaction mixture was quenched by pouring into 250 mL of ice water. The aqueous solution was extracted with CHC13 (3 x 100 mL), and the combined organic extracts were washed with 5% NaCl (100 mL), dried over MgSOa, and filtered. Concentration of the filtrate under reduce pressure 181 and purification of the residue by flash chromatography (hexane/ethyl acetate, 80/20) provided the product (1.2 g, 85%) as a yellow solid. TLC (80:20 hexane/ethyl acetate) Rf = 0.50. 1H NMR 8 0.84 (t, 3H), 1.18-l.35 (m, 14H), 1.60 (t, 2H), 2.58 (t, 2H), 7.04 (d, 1H), 7.38 (dd, 1H), 7.88 (d, 1H) 10.42 (s, 1H). 4-methyl-2-nitrophenol [CH3PhN020H] (9a) The crude product was obtained as described above without column purification. It was recrystallized from hexane to give a yellow solid in 69% yield. 1H NMR 8 2.33 (s, 3H), 7.04 (d, 1H), 7.38 (dd, 1H), 7.88 (d, 1H), 10.44 (s, 1H).‘9‘2° 4-ethy1-2-nitrophenol [CH3CH2PhN020H] (9b) The crude product was obtained as described above without column purification. It was recrystallized from hexane to give a yellow solid in 62% yield. 1H NMR 8 1.29 (t, 3H), 2.68 (q, 2H), 7.04 (d, 1H), 7.88 (d, 1H), 10.44 (s, 1H). 4-n-Propyl-2-nitrophenol [CH3(CH2)2PhN020H] (9c) Obtained as described in 9e as a yellow solid in 65% yield. TLC (70:30 hexane/ethyl acetate ) Rf = 0.52. 1H NMR 8 0.92 (t, 3H), 1.60 (m, 2H), 2.58 (t, 2H), 7.04 (d, 1H), 7.88 (d, 1H), 10.44 (s, 1H). 4-n-Heptyl-2-nitrophenol [CH3(CH2)6PhNOzOH] (9d) Obtained as described above as a yellow solid in 71% yield. TLC (90:10 hexane/ethyl acetate) Rf = 0.61. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 8H), 1.60 (m, 2H), 2.58 (t, 2H), 7.04 (d, 1H), 7.38 (dd, 1H), 7.88 (d, 111), 10.42 (s, 1H). 4-n-Tetradecyl-2-nitrophenol [CH3(CH2)13PhNOZOH] (91') Obtained as described above as a yellow solid in 80% yield. TLC (85: 15 hexane/ethyl acetate) Rf = 0.63. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 22H), 1.60 (t, 2H), 2.58 (t, 2H), 7.04 (d, 1H), 7.38 (dd, 1H), 7.88 (d, 1H) 10.42 (s, 1H). 182 4-n-Octadecyl-2-nitrophenol [CH3(CH2)17PhN020H] (9g) Obtained as described above as a yellow solid in 70% yield. TLC (85:15 hexane/ethyl acetate) Rf = 0.63. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 30H), 1.60 (t, 2H), 2.58 (t, 2H), 7.04 (d, 1H), 7.38 (dd, 1H), 7.88 (d, 1H) 10.42 (s, 1H). 4-n-Eicosyl-2-nitrophenol [CH3(CH2)19PhN020H] (9h) Obtained as described above as a yellow solid in 74% yield. TLC (85: 15 hexane/ethyl acetate) Rf = 0.63. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 34H), 1.60 (t, 2H), 2.58 (t, 2H), 7.04 (d, 1H), 7.38 (dd, 1H), 7.88 (d, 1H) 10.42 (s, 1H). 10 Attachment of the CIEOy chain 5-n-Decyl-2-(2,5,8-trioxadecan-10-oxy)nitrobenzene [CH3(CH2)9PhN02(OCH2CH2)3OCH3] (10e) Under a nitrogen atmosphere, 9e (1.1 g, 3.9 mmol) dissolved in a mixture of 200 mL of dry THF and DMSO (THF/DMSO = 4:1) was added to a refluxing solution of N aH (0.25 g, 10 mmol) in 50 mL anhydrous THF . After 20 minutes, l0-tosyloxy-2,5,8-trioxadecane (2.0 g, 6.3 mmol) in 100 mL dry THF was added drop-wise to the mixture. After refluxing overnight, the mixture was quenched with 300 mL of water, and the aqueous layer was separated and extracted with CHC13 (3 x 100 mL). The combined THF solution and CHC13 extracts were washed with saturated NaCl solution (3 x 150 mL), dried (MgSOa), and filtered. Concentration of the filtrate under reduced pressure followed by flash chromatography (hexane/ethyl acetate, 40:60) provided the product (0.98 g, 59%) as a light yellow oil. TLC (40:60 hexane/ethyl acetate) Rf: 0.48. 1H NMR 8 0.84 (t, 3H), 1.18—1.35 (m, 14H), 1.60 (t, 2H), 2.56 (t, 2H), 3.35 (s, 3H), 3.52 (m, 2H), 3.63 (m, 4H), 3.75 (m, 2H), 3.86(t, 2H), 4.21(t, 2H), 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H). 183 S-methyl-2-methoxynitrobenzene [CH3PhNOzOCH3] (10a) The crude product was obtained as described above without column purification. Except that CH3I is used instead of tosylated alcohol. The crude product was recrystallized from ether to give a yellow solid in 71% yield. 1H NMR 8 2.33 (s, 3H), 3.9l(s, 3H) 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H).'9'2' 5-ethyl-2-nitrophenol [CH3CH2PhN020CH3] (10b) The crude product was obtained as described above without column purification. The crude product was recrystallized from ether to give a yellow solid in 68% yield. 1H NMR 8 1.22 (t, 3H) 2.63 (q, 2H), 3.95(s, 3H) 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H). S-n-Propyl-2-(2-oxabutan-4-oxy)nitrobenzene [CH3(CH2)2PhN020CH2CH20CH3] (10c) Obtained as described in We as a yellow solid in 85% yield. TLC (90:10 hexane/ethyl acetate) Rf = 0.38. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 8H), 1.44-1.62 (m, 2H), 2.56 (t, 2H), 3.92 (s, 3H), 6.98 (d, 1H), 7.31 (dd, 1H), 2.64 (d, 1H). S-n-Heptyl-2-(2,5-dioxaheptan-7-oxy)nitrobenzene [CH3(CH2)5PhNOz(OCH2CH2)20CH3] (10d) Obtained as described above as a yellow oil in 82% yield. TLC (50:50 hexane/ethyl acetate) Rf = 0.32. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 8H), 1.60 (m, 2H), 2.56 (t, 2H), 3.35 (s, 3H), 3.52 (t, 2H), 3.47 (t, 2H), 4.22 (t, 2H), 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H). 5-n-Tetradecyl-2-(2,5,8,l1,14-pentaoxahexadecan-l6-oxy)nitrobenzene [CH3(CH2)13PhN02(OCH2CH2)5OCH3] (10f) Obtained as described above as a yellow oil in 56% yield. TLC (40:60 hexane/ethyl acetate) Rf = 0.16. 1H NMR 8 0.84 (t, 3H), 184 1.18-1.35 (m, 22H), 1.60 (t, 2H), 2.56 (t, 2H), 3.35 (s, 3H), 3.52 -3.86(t, 18H), 4.21(t, 2H), 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H). 5-n-Octadecyl-2-(2,5,8,l1,14,17-hexaoxanonadecan-19-oxy)nitrobenzene [CH3(CH2)17PhNO2(OCH2CH2)6OCH3] (10g) Obtained as described above as a yellow oil in 29% yield. TLC (30:70 hexane/ethyl acetate) Rf = 0.11. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 30H), 1.60 (t, 2H), 2.56 (t, 2H), 3.35 (s, 3H), 3.52 -3.86(t, 22H), 4.21(t, 2H), 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H). 5-n-Eieosyl-2-(2,5,8,l1,14,]7,19-heptaoxadocosan-22-oxy)nitrobenzene [CH3(CH2)19PhN02(OCH2CH2)7OCH3] (10h) Obtained as described above as a yellow solid in 45% yield. TLC (20:80 hexane/ethyl acetate) Rf = 0.09. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 34H), 1.60 (t, 2H), 2.56 (t, 2H), 3.35 (s, 3H), 3.52 -3.86(t, 22H), 4.21(t, 2H), 6.98 (d, 2H), 7.28 (dd, 1H), 7.60 (d, 1H). 11 Reduction of nitro to amino groups 5-n-Decy1-2-(2,5,8-trioxadecan-10-oxy)aniline [CH3(CH2)9PhNH2(OCH2CH2)3OCH3] (11e) Wet Raney nickel (0.2 g, 50% slurry in water) was added to a solution of 10e (0.98 g, 2.3 mmol) in 150 mL ethanol. The solution was deoxygenated by repeatedly applying a vacuum and backfilling with nitrogen. The solution was stirred under 80 psi H2 atmosphere overnight, and then filtered and concentrated under reduced pressure. The aniline product was obtained as a white solid (0.87 g, 96%) and was used in subsequent reactions without purification. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 14H), 1.55 (t, 2H), 2.43 (t, 2H), 3.35 (s, 3H), 3.52-3.85 (m, 10H), 4.12 (t, 2H), 6.50 (m, 2H), 6.70 (d, 1H). 185 S-methyl-Z-methoxyaniline [CH3PhNH20CH3] (11a) Obtained as described above as a white solid in 99% yield. 1H NMR 8 2.21 (s, 3H), 3.80 (s, 3H), 3.50 (b, 2H), 6.50 (m, 2H), 6.70 (d, 1H).22 5-ethyl-2-methoxyaniline [CH3CH2PhNH20CH3] (1 lb) Obtained as described above as a white solid in 99% yield. 1H NMR 8 1.19 (t, 3H) 2.50 (q, 2H), 3.80 (s, 3H), 3.50 (b, 2H), 6.50 (m, 2H), 6.70 (d, 1H). 5-n-Propyl-2-(2-oxabutan-4-oxy)aniline [CH3(CH2)2PhNH2OCH2CH20CH3] (11c) Obtained as described above as a white solid in 99% yield. 1H NMR 8 0.92 (t, 3H), 1.60 (m, 2H), 2.43 (t, 2H), 3.42 (s, 3H), 3.75 (t, 2H), 4.12 (t, 2H), 6.50 (m, 2H), 6.70 (d, 1H). S-n-Heptyl-2-(2,5-dioxaheptan-7-oxy)aniline [CH3(CH2)6PhNH2(OCH2CH2)2OCH3] (11d) Obtained as described above as a white solid in 98% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 8H), 1.55 (t, 2H), 2.43 (t, 2H), 3.35 (s, 3H), 3.52-3.85 (m, 6H), 4.12 (t, 2H), 6.50 (m, 2H), 6.70 (d, 1H). 5-n-Tetradecyl-2-(2,5,8,11,14-pentaoxahexadecan-16-oxy)aniline [CH3(CH2)13PhNH2(OCH2CH2)5OCH3] (11f) Obtained as described above as a white solid in 100% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 22H), 1.55 (t, 2H), 2.43 (t, 2H), 3.35 (s, 3H), 3.52-3.85 (m, 18H), 4.12 (t, 2H), 6.50 (m, 2H), 6.70 (d, 1H). 5-n-Octadeeyl-2-(2,5,8,11,14,17-hexaoxanonadecan-19-oxy)aniline [CH3(CH2)17PhNH2(OCH2CH2)50CH3] (1 lg) Obtained as described above as a white solid in 99% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 30H), 1.55 (t, 2H), 2.43 (t, 2H), 3.35 (s, 3H), 3.52-3.85 (m, 22H), 4.12 (t, 2H), 6.50 (m, 2H), 6.70 (d, 1H). 186 5-n-Eicosyl-2-(2,5,8,l1,14,17,l9-heptaoxadocosan-ZZ-oxy)aniline [CH3(CH2)19PhNH2(OCH2CH2)-;OCH3] (11h) Obtained as described above as a white solid in 98% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 34H), 1.55 (t, 2H), 2.43 (t, 2H), 3.35 (s, 3H), 3.52-3.85 (m, 22H), 4.12 (t, 2H), 6.50 (m, 2H), 6.70 (d, 1H). 12 Protection of aniline derivatives S-n-Decyl-2-(2,5,8-trioxadecan-10-oxy)-N-acetylaniline [CH3(CH2)gPhNHAc(OCH2CH2)3OCH3] (12e) Acetic anhydride (5 mL) was added to lle (0.87 g, 2.2 mmol). The mixture was stirred at 60 °C for 2 hours, cooled to room temperature, and then stirred under high vacuum overnight to remove residual acetic anhydride. The acetylated product was obtained as a white solid (0.91 g, 95%) and was used in subsequent reactions without purification.23 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 14H), 1.55 (t, 2H), 2.18 (s, 3H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.80 (m, 10H), 4.12 (t, 2H), 6.76 (s, 2H), 8.16 (s, 1H), 8.32 (s, 1H). 5-methyl-2-methoxy-N-acetylaniline [CH3PhNHAcOCH3] (12a) Obtained as described above as a white solid in 100% yield. 1H NMR 8 2.18 (s, 3H), 2.28 (s, 3H), 3.84 (s, 3H), 6.76 (m, 2H), 7.71 (b, 1H), 8.18 (s, 1H).23 S-ethyl-2-methoxy-N-acetylaniline [CH3CH2PhNHAcOCH3] (12b) Obtained as described above as a white solid in 100% yield. 1H NMR 8 1.20 (t, 3H), 2.18 (s, 3H), 2.56 (q, 2H), 3.84 (s, 3H), 6.80 (m, 2H), 7.72 (b, 1H), 8.25 (s, 1H). 5-n-Propyl-2-(2-oxabutan-4-oxy)-N-acetylaniline [CH3(CH2)2PhNHAcOCH2CH2OCH3] (12c) Obtained as described above as a white solid in 100% yield. 1H NMR 8 0.92 (t, 3H), 1.60 (m, 2H), 2.18 (s, 3H), 2.52 (t, 2H), 3.42 (s, 3H), 3.75 (t, 2H), 4.12 (t, 2H), 6.76 (s, 2H), 8.16 (s, 1H), 8.32 (s, 1H). 187 S-n-Heptyl-2-(2,5-dioxaheptan-7-oxy)-N-acetylaniline [CH3(CH2)6PhNHAc(OCH2CH2)2OCH3] (12d) Obtained as described above as a white solid in 100% yield. 1H NMR 8 0.84 (t, 3H), 1.18—1.35 (m, 8H), 1.55 (t, 2H), 2.18 (s, 3H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.80 (m, 6H), 4.12 (t, 2H), 6.76 (s, 2H), 8.16 (s, 1H), 8.32 (s, 1H). 5-n-Tetradecyl-2-(2,5,8,11,14-pentaoxahexadecan-l6-oxy)-N-acetylaniline [CH3(CH2)13PhNHAc(OCH2CH2)5OCH3] (12f) Obtained as described above as a white solid in 100% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 22H), 1.55 (t, 2H), 2.18 (s, 3H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.80 (m, 181-I), 4.12 (t, 2H), 6.76 (s, 2H), 8.16 (s, 1H), 8.32 (s, 1H). 5-n-Octadecyl-2-(2,5,8,l1,14,17-hexaoxanonadeean-l9-oxy)-N-acetylaniline [CH3(CH2)17PhNHAc(OCH2CH2)60CH3] (12g) Obtained as described above as a white solid in 100% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 30H), 1.55 (t, 2H), 2.18 (s, 3H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.80 (m, 22H), 4.12 (t, 2H), 6.76 (s, 2H), 8.16 (s, 1H), 8.32 (s, 1H). 5-n-Eicosy1-2-(2,5,8,1 1,14,17,19-heptaoxadocosan-22-oxy)-N-acetylaniline [CH3(CH2)19PhNHAc(OCH2CH2)-;OCH3] (12h) Obtained as described above as a white solid in 100% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.35 (m, 34H), 1.55 (t, 2H), 2.18 (s, 3H), 2.52 (t, 2H), 3.35 (s, 3H), 3.52-3.80 (m, 22H), 4.12 (t, 2H), 6.76 (s, 2H), 8.16 (s, 1H), 8.32 (s, 1H). 13 Nitration of protected anilines 5-n-Decyl-2-(2,5,8-trioxadecan-10-oxy)-4-nitro-N-acetylaniline [CH3(CH2)9PhNHAcN02(OCHzCH2)3OCH3] (13c) During a 5 minute period, 188 concentrated sulfuric acid (lmL) was added to a stirred solution of 12e (0.91 g, 2.1 mmol) in 7 mL glacial acetic acid at 5 °C. , The solution was cooled to 0 °C, and 1 mL of I'INO3 (75 %) was added during 5 minutes. The mixture was allowed to warm to room temperature, and after 5 mins, the solution was poured into 70 mL ice water. The aqueous solution was extracted with CHC13 (3 x 70 mL) and the combined organic extracts were washed with 5% NaOH (2 x 50 mL), dried over MgSO4, filtered, and concentrated under reduced pressure. The product (0.87 g, 87%) was isolated as a dark yellow solid and was used in subsequent steps without purification.24 1H NMR 8 0.84 (t, 3H), 1.18-1.4 (m, 14H), 1.58 (t, 2H), 2.22 (s, 3H), 2.85 (t, 2H), 3.35 (s, 3H), 3.50-3.75 (m, 8H), 3.86 (t, 2H), 4.20 (t, 2H), 7.56 (s, 1H), 8.40 (s, 1H), 8.60 (s, 1H). S-Methyl-2-methoxy-4-nitro-N-acetylaniline [CH3PhNHAcN020CH3] (13a) Obtained as described above as a yellow solid in 72% yield. 1H NMR 8 2.20 (s, 3H), 2.55 (s, 3H), 3.94 (s, 3H), 7.60 (s, 1H), 7.98 (b, 1H), 8.40 (s, 1H). S-Ethyl-2-methoxy-4-nitro-N-acetylaniline [CH3CH2PhNHAcN020CH3] (13b) Obtained as described above as a yellow solid in 78% yield. 1H NMR 8 1.21 (t, 3H), 2.21 (s, 3H), 2.90 (q, 2H), 3.92 (s, 3H), 7.52 (s, 1H), 7.90 (b, 1H), 8.40 (s, 1H). S-n-Propyl-2-(2-oxabutan-4-oxy)-4-nitro-N-acetylaniline [CH3(CH2)2PhNHAcN020CH2CH2OCH3] (13c) Obtained as described above as a dark yellow solid in 62% yield. 1H NMR 8 0.92 (t, 3H), 1.60 (m, 2H), 2.22 (s, 3H), 2.85 (t, 2H), 3.42 (s, 2H), 3.75 (t, 2H), 4.20 (t, 2H), 7.56 (s, 1H), 8.40 (s, 1H), 8.60 (s, 1H). S-n-Heptyl-2-(2,5-dioxaheptan-7-oxy)-4-nitro-N-acetylaniline [CH3(CH2)6PhNHAcN02(OCH2CH2)2OCH3] (13d) Obtained as described above as a dark yellow solid in 51% yield. 1H NMR 8 .84 (t, 3H), 1.18—1.40 (m, 8H), 1.58 (m, 2H), 189 2.22 (s, 3H), 2.85 (t, 2H), 3.35 (s, 3H), 3.55 (t, 2H), 3.70 (t, 2H), 3.85 (t, 2H), 7.60 (s, 1H), 8.2 (b, 1H), 8.42 (s, 1H). 5-n-Tetradecyl-2-(2,5,8,l1,14-pentaoxahexadecan-l6-oxy)-4-nitro-N- acetylaniline [CH3(CH2)13PhNHAcN02(OCH2CH2)50CH3] (13f) Obtained as described above as a dark yellow solid in 96% yield. lH NMR 8 0.84 (t, 3H), 1.18-1.4 (m, 22H), 1.58 (t, 2H), 2.22 (s, 3H), 2.85 (t, 2H), 3.35 (s, 3H), 3.50-3.86 (t, 18H), 4.20 (t, 2H), 7.56 (s, 1H), 8.40 (s, 1H), 8.60 (s, 1H). S-n-Octadecyl-Z-(2,5,8,l1,14,17-hexaoxanonadecan-l9-oxy)-4-nitro-N- acetylaniline [CH3(CH2)17PhNHAcN02(OCH2CH2)5OCH3] (13g) Obtained as described above as a dark yellow solid in 100% yield. 1H NMR 8 0.84 (t, 3H), 1.18-l.4 (m, 30H), 1.58 (t, 2H), 2.22 (s, 3H), 2.85 (t, 2H), 3.35 (s, 3H), 3.50-3.86 (t, 22H), 4.20 (t, 2H), 7.56 (s, 1H), 8.40 (s, 1H), 8.60 (s, 1H). 5-n-Eicosyl-2-(2,5,8,l1,14,17,19-heptaoxadocosan-22-oxy)-4-nitro-N- acetylaniline [CH3(CH2)lgPhNHAcN02(OCH2CH2)-;OCH3] (13h) Obtained as described above as a dark yellow solid in 88% yield. 1H NMR 8 0.84 (t, 3H), 1.18-1.4 (m, 34H), 1.58 (t, 2H), 2.22 (s, 3H), 2.85 (t, 2H), 3.35 (s, 3H), 3.50-3.86 (t, 26H), 4.20 (t, 2H), 7.56 (s, 1H), 8.40 (s, 1H), 8.60 (s, 1H). 14 Deprotection of aniline derivatives to give CxPhNEOyCr S-n-Decyl-2-(2,5,8-trioxadecan-10-oxy)-4-nitroaniline [CH3(CH2)9PhNH2NO2(OCH2CH2)3OCH3] (Me) To 20 mL of 40% NaOH were added 13c (0.87 g, 1.8 mmol) and several drops of DMSO. The mixture was heated to 85 °C with stining for 2 hours, then was poured into 100 mL of ice cooled water and extracted with CHC13 (3 x 50 mL). The combined organic extracts were washed with saturated 190 NaCl solution (2 x 50 mL), dried over MgSO4, filtered and concentrated under reduced pressure. Purification by flash chromatography (20:80 hexane/ethyl acetate) followed by recrystallization from ether gave the product (0.72 g, 91%) as a bright yellow solid.25 mp 56.1 °C. TLC (20:80 hexane/ethyl acetate ) Rf = 0.31. 1H NMR 8 0.85 (t, 3H), 1.23-1.33 (m, 14H), 1.55 (m, 2H), 2.84 (t, 2H), 3.37 (s, 3H), 3.52-3.83 (m, 10H), 4.16 (t, 2H), 4.2- 5.0 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C23H4006N2 440.2886, found 440.2883. S-methyl-2-methoxy-4-nitroaniline [CHgPhNH2N02OCH3] (14a) Obtained as described above as a bright yellow solid in 72% yield. mp 132.4 °C (lit.26 mp 132 °C). TLC (80:20 hexane/ethyl acetate) Rf = 0.28.1H NMR 8 2.52 (s,3H), 3.88 (s, 3H), 4.35 (b, 2H), 6.46 (s, 1H), 7.62 (s, 1H). HRMS calc. for C3H1003N2 182.0691, found 182.0687. S-ethyl-2-methoxy-4-nitroaniline [CH3CH2PhNH2NO2OCH3] (14b) Obtained as described above as a bright yellow solid in 78% yield. mp 100.6 °C. TLC (80:20 hexane/ethyl acetate) Rf = 0.27. 1H NMR 8 8 1.21 (t, 3H), 2.18 (s, 3H), 3.89 (s, 3H), 4.35 (b, 2H), 6.46 (s, 1H), 7.62 (s, 1H). HRMS calc. for C9H1203N2 196.0848, found 196.0843. 5-n -Propyl-2-(2-oxabutan-4-oxy)-4-nitroaniline [CH3(CH2)2PhNH2,NO2OCH2CH20CH3] (14c) Obtained as described above as a bright yellow solid in 81% yield. mp 91.2 °C. TLC (70:30 hexane/ethyl acetate) Rf = 0.33.1H NMR 8 0.95 (t, 3H), 1.58 (m, 2H), 2.84 (t,2H), 3.42 (s, 3H), 3.75 (t, 2H), 4.16 (t, 2H), 4.50 (b, 2H), 6.44 (s, 1H), 7.62 (s, 1H). HRMS calc. for C(2H1304N2 254.1267, found 254.1278. 191 1 5-n-Heptyl-2-(2,5-dioxaheptan-7-oxy)-4-nitroaniline [CH3(CH2)5PhNH2NO2(OCH2CH2)2OCH3] (14d) Obtained as described above as a bright yellow solid in 80% yield. mp 76.2 °C. TLC (50:50hexane/ethyl acetate) Rf = 0.52.1H NMR 8 0.85 (t, 3H), 123-1.33 (m, 8H), 1.55 (m, 2H), 2.84 (t, 2H), 3.37 (s, 3H), 3.55 (t, 2H), 3.68 (t, 2H), 3.85 (t, 3H), 4.20 (t, 2H), 4.20-5.00 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C13H3005N2 354.2155, found 354.2147. 5-n-Tetradecyl-2-(2,5,8,l1,14-pentaoxahexadecan-16-oxy)-4-nitroaniline [CH3(CH2)13PhNH2N02(OCH2CH2)50CH3] (14f) Obtained as described above as a bright yellow solid in 66% yield. mp 56.0 °C. TLC (ethyl acetate) Rf = 0.14.1H NMR 8 0.85 (t, 3H), 1.23-1.33 (m, 22H), 1.55 (m, 2H), 2.84 (t, 2H), 3.37 (s, 3H), 3.52-3.83 (m, 18H), 4.16 (t, 2H), 4.2-5.0 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C31H5603N2 584.4037, found 584.4036. 5-n-Octadecyl-2-(2,5,8,l1,14,17-hexaoxanonadecan-19-oxy)-4-nitroaniline [CH3(CH2)17PhNH2NO2(OCH2CH2)GOCH3] (14g) Obtained as described above as a bright yellow solid in 85% yield. mp 60.1 °C. TLC (ethyl acetate) Rf = 0.10.1H NMR 8 0.85 (t, 3H), 1.23-1.33 (m, 30H), 1.55 (m, 2H), 2.84 (t, 2H), 3.37 (s, 3H), 3.52-3.83 (m, 22H), 4.16 (t, 2H), 4.2-5.0 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C37H6309N2 684.4925, found 684.4915. 5-n-Eicosyl-2-(2,5,8,l1,14,17,l9-heptaoxadocosan-Z2-oxy)-4-nitroaniline [CH3(CH2)19PhNH2N02(OCH2CH2)7OCH3] (14h) Obtained as described above as a bright yellow solid in 88% yield. mp 58.5 °C. TLC(ethyl acetate) Rf = 0.08. 1H NMR 8 0.85 (t, 3H), 1.23-1.33 (m, 34H), 1.55 (m, 2H), 2.84 (t, 2H), 3.37 (s, 3H), 3.52-3.83 (m, 192 26H), 4.16 (t, 2H), 4.2-5.0 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C41H76010N2 756.5500, found 756.5510. 15 Dimethylation of aniline derivatives S-n-Decyl-2-(2,5,8-trioxadecan-10-oxy)-4-nitro(N,N-dimethyl)aniline [CH3(CH2)10PhN(CH3)2N02(OCH2CH2)3OCH3] (15a) To a solution of 14a (0.030 g, 0.07 mmol) in 2 mL DMSO was added 1.0 mL CH3I and 0.5 g of KOH. The mixture was stirred at room temperature for 1.5 h, diluted with 50 mL of water, and extracted with CHC13 (2 X 20 mL). The combined organic extracts were washed with 5% NaCl (2 X 20 mL), dried over MgSO4, filtered, and concentrated at reduced pressure. Flash chromatography (50:50 hexane/ethyl acetate) gave the final product (0.030g, 90%) as a yellow oil.27 TLC (50:50 hexane/ethyl acetate) 12. = 0.52. ‘H NMR 5 0.85 (t, 3H), 1.23- 1.37 (m, 14H), 1.57 (m, 2H), 2.87 (t, 2H), 2.95 (s, 6H), 3.35 (s, 3H), 3.51 (m, 2H), 3.61- 3.71 (m, 6H), 3.88 (t, 2H), 4.16 (t, 2H), 6.53 (s, 1H), 7.58 (s, 1H). 5-n-Tetradecyl-2-(2,5,8,l1,14-pentaoxahexadecan-l6-oxy)-4-nitro(N,N- dimethyl)aniline [CH3(CH2)13PhN(CH3)2N02(OCH2CH2)5OCH3] (15b) Obtained as described above as a yellow solid in 83% yield. TLC (ethyl acetate) Rf = 0.14. 1H NMR 8 0.85 (t, 3H), 123-1.37 (m, 24H), 1.57 (m, 2H), 2.87 (t, 2H), 2.95 (s, 6H), 3.35 (s, 3H), 3.52-3.83 (m, 18H), 4.16 (t, 2H), 4.2-5.0 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C33H6003N2 612.4350, found 612.4347. 5-n-Eicosyl-2-(2,5,8,l1,14,17,19-heptaoxadocosan-ZZ-oxy)-4-nitro(N,N- dimethyl)aniline [CH3(CH2)19PhN(CH3)2N02(0CH2CH2)7OCH3] (15c) Obtained as described above as a yellow solid in 80% yield. TLC (ethyl acetate) Rf = 0.08. 1H NMR 8 0.85 (t, 3H), 1.23-1.37 (m, 34H), 1.57 (m, 2H), 2.87 (t, 2H), 2.95 (s, 6H), 3.35 (s, 3H), 193 3.52-3.83 (m, 26H), 4.16 (t, 2H), 4.2-5.0 (b, 2H), 6.43 (s, 1H), 7.63 (s, 1H). HRMS calc. for C43H80010N2 784.5836, found 784.5813. 16 Synthesis of didecyl substituted p-nitroaniline 1,4-n-Didecylbenzene [CH3(CH2)9Ph(CH2)9CH3] (16) Obtained using the processure for 6a as a white crystalline solid in 99% yield, except that two equivalents of decylbromide and the Ni catalyst were used. mp 30.5 °C. (lit.28 mp 28.7-29.1 °C ).'H NMR (300 MHz, CDC13) 8 0.85 (t, 6H), 1.18-1.32 (b, 28H), 1.55 (t, 4H), 2.52 (t, 4H), 6.80 (d, 2H), 7.08 (d, 2H). 2,6-n-Didecyl-nitrobenzene [CH3(CH2)9PhN02(CH2)9CH3] (17) Obtained as described in 9e as a yellow oil in 89% yield. TLC (hexane) Rf = 0.31. 1H NMR 8 0.85 (t, 6H), 1.23-1.37 (m, 24H), 1.40-1.64 (m, 4H), 1.82 (m, 2H), 2.55 (t, 2H), 4.05 (t, 2H), 6.95 (d, 1H), 7.30 (q, 1H), 7.62 (d, 1H). 2,6-n-Didecylaniline [CH3(CH2)9PhNH2(CH2)9CH3] (18) Obtained as described in He as a white solid in 100% yield. 1H NMR 8 0.84 (m, 6H), 1.15-1.62 (m, 28H), 1.75 (m, 2H), 2.45 (t, 2H), 3.95 (t, 2H), 6.50 (m, 2H), 6.68 (d, 1H). 2,6-n-Didecyl-N-acetylaniline [CH3(CH2)9PhNHAc(CH2)9CH3] (19) Obtained as described in 12e as a white solid in 100% yield. 1H NMR 8 0.84 (m, 6H), 1.15-1.60 (m, 28H), 1.78 (m, 2H), 2.16 (s, 1H), 2.52 (t, 2H), 3.98 (t, 2H), 6.75 (m, 2H), 7.70 (b, 1H), 8.20 (s, 1H). 2,6-n-Didecyl-4-nitro-N-acetylaniline [CH3(CH2)9PhNHAcNO2(CH2)9CH3] (20) Obtained as described in l3e as a yellow solid in 88% yield.lH NMR 8 0.84 (m, 6H), 1.15-1.62 (m, 28H), 1.84 (m, 2H), 2.22 (s, 3H), 2.85 (t, 2H), 4.08 (t, 2H), 7.48 (s, 1H), 8.40 (s, 1H). 194 2,6-n-Didecyl-4-nitroaniline [CH3(CH2)9PhNH2N02(CH2)9CH3] (21) Obtained as described in 14c as a yellow solid in 88% yield. TLC (90: 10 hexane/ethyl acetate) Rf = 0.32. mp 66.1 °C. 1H NMR 8 0.84 (m, 6H), 1.18-1.62 (m, 28H), 1.80 (m, 2H), 2.84 (t, 2H), 4.02 (t, 2H), 4.35 (b, 2H), 6.44 (s, 1H), 7.55 (s, 1H). HRMS calc. for C26H4602N2 418.3559, found 418.3542. 195 4.4 (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) References Borjesson, L.; Weleh, C. J. Acta Chem. Scand. 1991, 45, 621-626. Markovskii, L. N .; Rudkevich, D. M.; Kalchenko, V. I. Zhumal Org. Khimii 1990, 26, 452-453. Nabeshima, T.; Hosoya, T.; Yano, Y. Synlett 1998, 265-266. Bauer, H.; Briaire, J .; Staab, H. A. Tetrahedron Lett. 1985, 26, 6175-6178. Asakawa, M.; Ashton, P. R.; Balzani, V.; Credi, A.; Mattersteig, G.; Matthews, 0. A.; Montalti, M.; Spencer, N.; Stoddart, J. F.; Venturi, M. Chem. -Eur. J. 1997, 3, 1992-1996. Kocian, O.; Chiu, K. W.; Demeure, R.; Gallez, B.; Jones, C. J.; Thomback, J. R. J. Chem. Soc.-Perkin Trans. 1 1994, 527-535. Takahashi, H.; Kuwamura, T. Bull. Chem. Soc. 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Tetrahedron 1992, 48, 2919- 2924. Fischer, A.; Henderson, G. N.; RayMahasay, S. Can. J. Chem. 1987, 65, 1233- 1240. Neumeyer J. Med. Chem. 1977, 20, 894. Burger, M. J. Am. Chem. Soc. 1940, 62, 1079-1083. Dadswell; Kenner J. Chem. Soc. 1927, 584. Kishner; Hrasowa; Anilinokr Chem. Zentralbl. 1934, 105, 2354. Kolbah, D. Helv. Chim. Acta 1977, 60, 265-283. Johnstone, R. A. W.; Rose, M. E. Tetrahedron 1979, 35, 2169-2173. Haedicke, B.; Schlenk, W. Justus Liebigs Ann. Chem. 1972, 764, 103-111. 197 M IIIIIIIIIIIIIIIIIIIIIIIIIIIIII JIM11lfllfllflljulflflwaflfléMIMI“!!!