Propargyl and 1,1-dimethyl propargyl substituted poly(ethyleneoxides) (propargyl substituted = poly(PGE), 1,1ʹ-dimethyl propargyl substituted = poly(MGE)) have been prepared by ring-opening polymerization of epoxides, which were synthesized from epichlorohydrin and propargyl or 1,1-dimethyl propargyl alcohol via Williamson ether synthesis. The resulting polymers were modified by Cu-catalyzed azide alkyne cycloaddition (CuAAC) of the polymer propargyl groups and organic azides. When these reactions were carried out with mixtures of azides, the ratios of azides incorporated in the polymer side chains were equal to the molar ratios of the organic azides reactants (± 2%). Mixtures of hydrophobic (decyl azide) and hydrophilic (mDEG azide) azides result in amphiphilic polymers that exhibited a lower critical solution temperature (LCST) behavior. The polymer LCSTs scaled from 48 to 97 ± 2 °C (poly(PGE) derived amphiphiles) and 4 to 46 ± 1 °C (poly(MGE) derived amphiphiles) in a roughly linear fashion with the mole fraction of hydrophilic side chains in the polymer. When charged azides, COOH azide and aminium azide, were used, the physical property as well as the LCST behavior oh the polymers were changed. The LCSTs of polymers incorporating charged azides were increased and the LCSTs were decreased by adding salts in the solutions. The hydrodynamic radii (RH) obtained from DLS measurements indicate that polymers form unimolecular micelles in water (Mn = 52,000 g/mol, PDI = 1.19, RH = 6 ± 2 nm), and TEM data showed monodisperse domains (20 ± 4 nm, for Mn = 52,000) when water was evaporated at room temperature from solutions cast on TEM grids. This length scale is consistent with domains that consist of single polymer chains. When the TEM grid was heated during evaporation, the domain size increased to 74 ± 45 nm. In solution, the unimolecular micelles can solubilize hydrophobic small molecules, such as trans-azobenzene (trans-PhN=NPh) in water. DLS data suggested that polymer encapsulating trans-PhN=NPh (trans-PhN=NPh@poly(PGE) or poly(MGE)) derived amphiphiles) showed signs of aggregation in one case (RH = 12 ± 8 nm) and no signs of aggregation in another case (RH = 5 ± 2 nm). When the resulting solutions were raised above the polymer LCST the polymer and small molecule precipitated. When the mixture was cooled below the LCST, the polymer and hydrophobic small molecule re-dissolved. The unimolecular micelles were used to encapsulate a hydrophilic macromolecule, Subtilisin Carlsberg (SC), in aqueous solution and organic media. Poly(PGE) or poly(MGE) derived amphiphiles with COOH pendant group slowed down SC aggregation in aqueous environment. Also, the activity of SC@poly(MGE) derived amphiphiles with COOH pendant group was assayed and the half-life of SC was increased to 10 h from 2 h at 50 °C. Initial studies of SC@poly(PGE) or poly(MGE) derived amphiphiles in organic media showed enzymatic activity in toluene after 16 h at 37 °C.
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