CHIMICAL STUDIES OF THE CQPOLYMER OF STYRENE AND MALHC AHHYDMDE "Flu-sis {w the Degree cf M. S. MICHIQAN STATE COLLEGE Ruben Emmett Byma, Jr. 1933 31-795 This is to certify that the thesis entitled CHEMICAL STUDIES OF THE COPOLYMER OF STYRENE AND MALEIC ANHYDRIDE presented by Robert. Emmett Byrne, Jr. has been accepted towards fulfillment of the requirements for M.S ' degree inghemlfirp: fic % z [L4 .ajor professor I h“ Date—MM“ V- . |_..,____..._ ... .. ._-..__._..._..__l CHEMICAL STUDIES OF THE COPOLYKER OF STYREYE AID HALFIC ANHYDHIDE by ROBERT EIEETT BYRNE, JR. A TEESI Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 19h9 “fil? " BC? 9:;- ACKNOWLEDGEENT The author wishes to express his appreciation to Ralph L. Guile for his guidance and encouragement and to Kenneth G. Stone and Robert M. Herbst for their helpful suggestions and criticism. :3 ya. C: S? IQ U] TABLE OF CONTENTS Introduction Historical Experimental Preparation of the copolymer Determination of percent anhydride Molecular weight determination Solubility of the copolymer Preparation of salts from the copolymer Preparation of the free acid c0polymer Preparation A Preparation B Esterification with methyl alcohol Preparation A Preparation B Preparation C Preparation D Esterification with ethyl alcohol Preparation A Preparation B Esterification with n—butyl alcohol Esterification with n-amyl alcohol Preparation A Preparation B Reaction with thionyl chloride Preparation A ii CAUIJI“ 10 10 ll ll 12 13 13 ll; 16 Preparation B Preparation of the amine of the c0polymer Preparation A Preparation B Preparation C Reaction with hydrazine Potentiometrio titrations Saponification of esterified materials Discu3"on I t— Conclusions Literature cited 16 17 17 17 18 19 21 23 33 3h INTRODUCTION The literature is almost entirely lacking in any study of the chemical properties of the c0polymer of styrene and maleic anhydride.. As a part of a continuing investigation in this laboratory1 the study herein described was initiated in an attempt to elucidate some of the chemical reactions of the copolymer. Since many linear polymers of high molecular weight exhibit reactivity dependent upon functional groups present in the polymer, this particular copolymer was inves— tigated as to reactions typical of acid anhydrides. The hydrolyzed form of the copolymer was investigated as to the prOperties of an acid. In most cases attempts were made to use standard analytical methods in identifying products. HISTOIICAL One of the first studies of the c0polymerization of maleic anhydride and styrene, as well as other ethylenic hydrocarbons, is reported by wagner—Jauregg‘. He prepcsed that the structural unit of the reaction product of maleic anhydrith with stilhene was- .4._c cH- cH- CH- ch:-- :C d 'dlc\ z° J in which the two components were combined in equimclar proportion. It was also stated that benzalfluorene gave a product in which the ratio of monomer units was 1:1 even though the initial concentration of the reac- ting monomers was varied. The addition of styrene to diethylmaleate, on the other hand, was found to yield a product in which the ratio of styrene to ester was 5:1. This ras further substantiated by Alfrey and Herz3 and Mayo an ad his co—worke ers“ who state that "for styrene-diethylmale- ate, polymer compos Hi ions lay very close to polys+ yrene." The relative unreactivity of diethylmaleate comp -ared to maleic anhydride is explains by Alfrey who assures that while the ethylenic bond in the anhydride is relatively expos d, the bond in diethylmaleate is protected from reaction by the presence of bulky carboethoxy groups. Similar unreactive character is exhibited to a somewhat lesser degree by diethylchloromaleate. Derivatives of the c0polyuer which are described in the literature 5’6’7’8’9’10’11’12 are limited largely to the monosodi 1m salt and the monoammonium salt. Directions for the preparation of a "partially esteri- fied" c0polymer are given in a U. S. patent6 and a German patentlg. 7 Some es ster rs of the copolymer have been ore‘arei 2‘ 3 by the cepolymeri- zation of styrene with diallyl and divinyl esters of maleic acid. These, however, do not correspond to esters which have been prepared by the author. They represent another approach to the study of the derivatives of the c0polymer. It is interesting to note that the copolymerization of styrene with the esters of fumaric acid is easily accomplishedh. EXPERIMENTAL REAGENTS: Styrene: The inhibited Dow Chemical Company product was purified by vacuum distillation and the fraction having an index of refraction of 1.5hh at 20°C was used. In some cases it was stored for several weeks at 5°C before being used. Maleic Anhydride: Eastman Kodak maleic anhydride was used. Several quantities of copolymer were prepared using anhydride which had been purified by distillation and no differences were noted in the resulting products. Benzoyl Peroxide: Eastman Kodak benzoyl peroxide was used without purification. Normal Amyl Alcohol: Normal amyl alcohol was purified by distillation collecting the fraction 135-1369C at 7h6mm pressure. Normal Butyl Alcohol: Normal butyl alcohol was purified by distillation collecting the fraction 116-117.S°C at 758mm pressure. Other Reagents: Commercially available C. P. grades were used. PREPARATION or THE COPOLYMERIO The reaction vessel was a one liter three-neck, round bottom flask with standard taper ground glass joints. It was fitted with a mechanical stirrer, a gas inlet tube and an addition tube in which were placed a thermometer and a reflux condenser. Twenty-six grams of styrene (0.25 mole), 2h.5g of maleic anhydride (0.25 mole) and 0.25g of benzoyl per- oxide (0.2 mole percent) were placed in the flask with 700ml of benzene. The mixture was stirred until dissolution was complete. The reaction S was carried out in a nitrogen atmosphere. The nitrogen used was first bubbled through alkaline pyrogallol to remove traces of oxygen which might inhibit the cepclymerization and then introduced below the surface of the reaction mixture. Heating was accomplished with an electric heat- ing mantle to bring the benzene to reflux(80°C). Reflux was maintained for two hours and the mixture was allowed to cool with stirring. The copolymer was collected by filtration and washed six times with small portions of benzene to remove polystyrene. The copolymer was air dried overnight(12 hours) and then dried at 90°C for several days. Micro car— bon-hydrogen determinations were made on the dry copolymer and the percent carbon was found to be 72.11, 70.01, 71.38 and 71.20. The values for hydrogen were 5.59, 5.07, h.81 and 5.03 percent. The calculated percent— age based on a structural unit containing one molecule of styrene to one molecule of maleic anhydride is 71.3 for carbon and h.98 for hydrogen. DETERMINATION OF THE PERCENT ANHYDRIDE IN THE COPOLYMERl3 A weighed sample of the c0polymer was dissolved in acetone and the solution was heated to about 25°C. Methyl alcohol was added in twice the amount theoretically necessary to form the half ester of the c0polymer. This sample was titrated with approximately 0.1N NaOH in methyl alcohol using phenolphthalein as the indicator. A second weighed sample of the cepolymer was dissolved in acetone, heated to about 25°C and titrated to the phenolphthalein end-point with approximately 0.lN aqueous NaOH. The mole percent anhydride was calculated to be 91.2. Sample calculation using 1.0g samples: Sample 1 Sample 2 2(meq aq. base - meq alc. base) meq aq. base Sample 1 Mole % anhydride X 100 2(9o80meq - 5-33mBQ) x 100 9.80meq 91.2% MOLECULAR WEIGHT Im'rmunNATION1h weighed samples of the 00polymer were dissolved in acetone and the resulting solution diluted to 100ml in a volumetric flask. These were cooled to 20°C k 0.1 in a constant temperature water bath. Viscosity measurements were made at the temperature of the bath with a Cannon- Fenske Ostwald viscosimeter. The time of efflux was measured with an electric timer. The relative viscosity,qr , was determined by comparing the time of efflux of the pure solvent with that of the c0polymer solution Y] = time of efflux of the solution V time of efflux of the solvent S . . : ‘.t? w; , . . _ . peeific V'LSCOSl ,, ,q” , as calculated from the relationship, 'lsP'Ylt l Concentration was expressed in grams of solute per 106ml of solution and the values were calculated for Y1“ lfi . A graph of fly/c versus C appears below. The average weight of the copolymer was found to be of the order of 36,300. See pageEHS for a discussion of this method.) VISCOSITY DATA Grams of copolymer per 190ml 0.0517 0.2Sh3 0.3912 Time of efflux in secs. 36.7 h3.7 h6.8 qv 1.0302 1.197 1.311; o o 0‘2 ] ESP- 0 0302 0 197 0 ,14 O. 3 O. 8 0.30 Yle/C- 5 5 73 A: Time of efflux of acetone 35.6 seconds «\EQQ\\%\ C°.\.\vd.\d~=UVN\OU eve m.% N6 b d + .r 11 010 $12 u use 5.: . E k. Vbtxqomou point. .51! uxbvtrx - Wlwwtk tutk Kt W330 3593.3. EQSQSQ \ NWQTQQ 50 ‘F ado . $6 1 Q.Q iv Won SOLUEILITY OF THE COPOLIHRL Solubility determinations on the copolymer were made in a qualitative way to ascertain which solvents might logically be employed in the various preparations. It was found that the c0polymer was easily soluble in ace- tone and methyl ethyl ketone; this was true of all the various forms of the c0polymer and its derivatives except for the basic salts. Solubility of the acid and anhydride forms of the copolymer was noted in basic sol- vents such as pyridine and aqueous alkali. The solution in aqueous alkali is undoubtedly due to the formation of the salts of the copolymer which are soluble in water. Some slight solubility of both the anhydride and acid forms of the copolymer in alcohols, dioxane and water was apparent. The acid form of the c0polymer was appreciably soluble in water if moist, but was difficultly soluble when dry. In dealing with macromolecules of this type, insollbility is a problem. Often lack of reaction is confused with lack of solubility. A polymer is said to be soluble in a given solvent if it swells after several hours contact and goes into solution completely in a day. PREPARATION OF SALTS FROM THE commas“ In the course of other preparations it appeared necessary to prepare salts of the copolymer. The sodium salt was prepared by treating the c0polymer with a calculated amount of aqueous NaOH based on a 1:1 styrene- maleic anhydride structural unit. It was isolated by pouring the dilute aqueous solution of the cepolymer salt into a relatively large volime of acetone in which the sodium salt was insoluble. Vigorous stirring was necessary to prevent the formation of lumps of the salt in acetone. The ammonium salt was prepared by dissolving the cepclymer, 5g, in an excess, 100ml, concentrated NHhOH. It was isolated by evaporating the resulting solution to dryness. A Kjeldahl analysis for nitrogen gave 5.62 and 5.37 percent compared to the value of 11.02 percent based on the structural unit containing two ammonium ions. The result, therefore, of the treat- ment with excess ammoniim hydroxide was the monoammonium salt. . 10 (K) PREPARATION OF THE FREE ACID FOE? 3? THE CDFOLIYER The free acid form of the cogolymer was prepared in two ways: Preparation A: The sodium or ammonium salt of the COpolymer in water was neutralized with reagent H31 in a Waring blender. The resulting materia was washed extensively with water until no test for the Cl ion was ob- tained from the washings. The product was finely divided and was suitable for use without grinding. When the material was prepared usin a mechani- ’,_1' Q cal stirrer, lumps formed during the neutralization and grinding was re— J paired before it could be used in subseguent reactions. Haterial prepared » n this manner was also very difficult to dry. FJ. ”d reparation 9: A dilute (approx. 55) solition of the copolymer in acetone was added slowly to a relatively large volume of water in a Waring blendor. The acid COpOlymer was washed with water to remove excess acetone. Analysis of products: Method a: Carbon—hydrogen determinations were carried out on the products from preparations A and E. Percentages of carbon found on the products from A were 65.92, 63.81 and 65.69. Hydrogen percentages on the same product were 5.57, b.62 and 5.76. The product from B showed 6b.66 and 63.96 percent carbon and 7.30 and b.37 percent hydrogen. The calculated values based on a 1:1 styrene-maleic acid structural unit are 65.55 Per- cent carbon and 5.h5 percent hydrogen. Method b: Determinations f the percent acid in the hydrolyzed c0polymer were made. Weighed samples of the cepolymer were dissolved in a measured excess of aqueous alkali. The excess base was titrated with standard HCl using phenolphthalein as the indicator. The percent acid cooolymer was calculated on the basis of the 1:1 structural unit. The values obtained were h6.3 and h3.6 percent. ll ESTERIFICATION WITH METHYL ALCOHOL The preparation of the methyl ester of the copolymer was attempted in several ways: Preparation A: In a 500ml three-neck, round bottom flask with ground glass standard taper joints fitted with a condenser, mechanical stirrer and a gas inlet tube below the surface of the liquid were placed 20g of the copolymer and 250ml of absolute methyl alcohol. The alcohol was heated to reflux while stirring and anhydrous HCl was allowed to flow through the system. After four hours of refluxing, a mass of polymer separated and 100 ml of absolute methyl alcohol was added to effect dis- solution. The polymer again separated after several minutes. The mix- ture was cooled and the polymer mass collected and dried at 100°C for 13 hours. The alcoholic solution in which the reaction had been carried out was evaporated to dryness and no residue remained. Preparation B: In a 500ml three-neck flask with ground glass standard taper joints fitted with a mechanical stirrer, dropping funnel with a gas inlet tube and a fractionating head were placed 5g of the copolymer and 100ml of absolute methyl alcohol. Stirring was started; anhydrous HCl was passed into the system and solution occurred rapidly. Distillate was collected from the fractionating head and the volume was kept constant by the addition of absolute methyl alcohol through the dropping funnel. After four hours at reflux, a polymer mass separated. Enough dioxane—l,h was added to dissolve the precipitate. Dioxane and absolute methyl al- cohol were mixed in equal proportions and the mixture was added dropwise to keep the volume constant. Refluxing was continued for 2h hours. The solution was evaporated to dryness under vacuum. The solid product was 12 dried in a vacuum oven at 70°C. Carbon-hydrogen determinations were made on the dry product. It was found to contain 66.h9, 66.h5, and 66.3h percent carbon and 6.07, 6.98 and 6.09 percent hydrogen. The calculated values based on the completely esterified 1:1 structural unit are 67.7h percent carbon and 6.h5 percent hydrogen. Preparation C: The copolymer, 50 was dissolved in a large excess, 250ml, Io) of absolute methyl alcohol and refluxed for four hours after going into solution. A solid was isolated by evaporating the solution to dryness. It was allowed to dry overnight at 100°C. A carbon-hydrogen analysis on the dry product showed 65.51, 63.89 and 65.30 percent carbon and 7.8h, h.73 and 5.00 percent hydrogen. The calculated values as stated above are 67.7h percent carbon and 6.h5 percent hydrogen. Preparation D: The copolymer, hg, which had been dried overnight under vacuum was dissolved in 100ml of absolute methyl alcohol. The absolute alcohol was prepared by adding metallic sodium to commercial absolute methyl alcohol and distilling the anhydrous alcohol directly into the reaction vessel. Solution of the COpOIymer required about ten hours during which time the mixture was stirred and heated to about 50°C. The reaction mixture was protected from moisture with calcium chloride. The product was isolated by evaporating the solution to dryness under vacuum. The solid product was then dried overnight in a vacuum oven at 70°C. Carbon- hydrogen determinations on the product showed 67.81 and 67.53 percent carbon and 6.70 and 6.79 percent hydrogen. Calculated values are 67.7h percent carbon and 6.h5 percent hydrogen. l3 ESTERIFICATION WITH ETHYL ALCOHOL The preparation of the ethyl ester of the copolymer was attempted in two ways: Preparation A: Four grams of the copolymer were dissolved in 100ml of absolute ethyl alcohol which were distilled directly into the reaction vessel from 200ml of absolute ethyl alcohol treated with 10g of sodium. The reaction mixture was protected from moisture. Solution of the c0poly- mer was complete in 1h hours, being aided by continuous stirring and heat- ing to about 50°C. A solid product was isolated by evaporating the alcohol solution under vacuum. The product was then dried at 70°C in a vacuum oven. Carbon-hydrogen determinations were made on the dry product and the percentages were 66.50 and 66.01 for carbon and 8.69 and 7.98 for hydrogen. The calculated values based on the completely esterified 1:1 structural unit are 67.13 percent carbon and 6.99 percent hydrogen. Preparation B: Five grams of the acid 00polymer were dissolved in 100ml 22 of purified dioxane :- 20ml, was added dropwise to the solution which was protected from moisture. (redistilled from sodium). Excess thionyl chloride, After solution was complete an excess of absolute ethyl alcohol (200ml) was added. A solid product was isolated by evaporating the solution under vacuum. It was dried for several hours in the vacuum oven at 70°C. Car- bon-hydrogen determinations on the dry product showed 66.53 and 66.7h percent carbon and 7.07 and 7.35 percent hydrogen. The calculated values as previously given are 67.13 percent carbon and 6.99 percent hydrogen. ESTERIFICATION WITH NORMAL BUTYL ALCOHOL In a 500ml three—neck, round bottom flask with ground glass standard taper joints fitted with a mechanical stirrer, a fractionating head and a dropping funnel with a gas inlet tube were placed 5g of the copolymer and 100ml of redistilled n—butyl alcohol.- Stirring, heating and the flow of anhydrous HCl through the system were begun and solution was rapid. Normal butyl alcohol was added dr0pwise and the volume was kept constant by distilling off solvent. The mixture was refluxed for 2h hours. Vacuum distillation was used to isolate the product which was then dried at 70°C in the vacuum oven. Carbon—hydrogen determinations on the dry product showed it to contain 66.79 and 66.87 percent carbon and 5.hh and 6.32 percent hydrogen. The values calculated on the basis of the completely esterified 1:1 structural unit are 7h.53 percent carbon and 8.70 percent hydrogen. 15 ESTERIFICATION WITH NORMAL AMYL.ALCOHOL Preparation A: The copolymer, 1g, was dissolved in 100 ml of redistilled n-amyl alcohol. The solution was heated near its boiling point (about 110°C) for two hours after dissolution was complete. The product was not isolated but was subjected to saponification in the alcohol solution. (See page 21) Preparation B: In a 500ml three-neck, round bottom flask with ground glass standard taper joints fitted with a mechanical stirrer, a fractionat- ing head and a dropping funnel with a gas inlet tube were placed 5g of cepolymer and 200ml of redistilled amyl alcohol. Stirring and heating were begun and when dissolution was complete (about twenty minutes) a stream of anhydrous hydrogen chloride was allowed to pass through the system. Reflux was maintained and the volume of solution kept constant for 2h hours by balancing distillation rate with the dr0pwise addition of alcohol. The solution was evaporated to dryness under vacuum. The product was dried in a vacuum oven at 85°C overnight. The material from this preparation was quite charred and was not subjected to carbon-hydro- gen analysis. (For saponification see page 21) l6 .EACTION flIT THI XYL CHLORIDE Preoaration A: In a 500ml round bottom flask with ground glass standard taper joints fitted with a condenser were placed 10g of the acid form of the copolymer and 75ml of thionyl chloride. The mixture was refluxed for 2h hours and some swelling occurred in the c0polymer. Excess thionyl chloride was removed under vacuum and the copolymer derivative stored in a des sicator over IIaOH pellets. T ;e ac1 d chloride was decomposed in a Parr bomb with sodium peroxide and potassium nitrate according to the method of Lemp and Eroder sonlé. An analysis for chlorine was made using the Volhard techniquel7. The product was found to contain h.89 and 2.25 percent chlorine. The calculated value based on the 1:1 strictural unit mt ir ing tw chlorine atoms per unit is 28.7L percent. Preparation B: The acid copolymer, lg, was dissolved in 100ml of dioxane- l,h in a 500ml round bottom flask with ground glass standard ta per joint. Twen y ml. of thionyl chloride was added dr0pwise. The reaction mixture was allowed to stand for six hours. Excess thionyl chloride and solvent were removed under vacuum, and the product was dried over NaOH pellets. A Parr bomb—Volhard chloride analysis showed 10.h8 and 11.21 percent chlorine. Another preparation of the acid chloride was made using the same technique. It was used in the preparation of the ethyl ester (see page 13). l7 PREPARATION OF THE AIIDE OF THE COPOLYMER Preparation A: The ammonium salt was prepared as previously described. It was subjected to baking at temperatures of from 120-185°C for periods ranging up to 25 days in attempts to rearrange the salt to the amide. Considerable charring was noted even at the shorter periods and lower temperatures. Hydrolysis of the products with cold aqueous NaOH gave a test for ammonials in all cases. The acidified solution yielded a product which gave no indication of nitrogen by the Lassaigne16 test. Pr paration B: The product of the treatment of the cepolymer vith methyl alcohol described in preparation A of that section was allowed to react with 30ml of liquid ammonia. A high pressure bomb was used as the reac- tion vessel and 8g of the partially esterified material were used. The temperature was raised to 120°C corresponding to a pressure of 550 pounds per square inch. The bomb was allowed to cool overnight, the reaction products removed and the resulting polymer was dried at 100°C for 2h hours to eliminate excess ammonia. A qualitative test for nitrogen, the Las— saigne test, on the product was positive. Treatment with aqueous alkali in the cold indicated the presence of ammonia. The acidified alkaline solution from the above test yielded a polymeric material which contained no nitrogen as indicated by the Lassaigne test. Preparation C: The partially esterified material from preparation A of the esterification with methyl alcohol was treated with concentrated NHLOH for three days. After evaporating the solution to dryness, the copolymer derivative was dried at 100°C overnight. A Kjeldahl analysis on the product showed 1.85 percent nitrogen. The calculated value is 12.8h percent nitrogen based on a 1:1 structural unit containing two anmmnium ions. 18 REACTION WITH HYDRAZINE The partially esterified material prepared with methyl alcohol as described in preparation A was allowed to react with hydrazine hydrate. Methyl alcohol was used as the solvent and 1.5g of the esterified material and 0.5g of hydrazine hydrate were used. Very little solution of the ester occurred and the mixture was allowed to go to dryness slowly on the steam bath. The resulting product was slightly soluble in water. A Kjeldahl analysis showed 8.LO, 5.35, and 5.62 percent nitrogen. The calculated value is 22.58 percent nitrogen for a 1:1 styrene-maleic acid unit containing two hydrazide groups. Bi NuE h». wN at: .‘Q Gk flux-W3: at“ NU.‘ QW