Polymerized Surfactant Vesicles. Determinations of Rates and Degrees of Polymerization in Vesicles Prepared from Styrene-Containing Surfactants

摘要

Rate constants (Eta/E values) for laser pulse initiated photopolymerization have been determined for 1200-2700-A-diameter bilayer surfactant vesicles prepared from dioctadecylmethyl(2-((4-vinylbenzoyl)-oxy)ethyl)ammonium bromide (3), from mixtures of dioctadecyldimethylammonium bromide (DODAB) and vinylbenzoic acid, from mixtures of 3 and DODAB, and from mixtures of 3 and vinylbenzoic acid. Pilots of polymerization rate constants aginst the mole fraction of 3 in vesicles prepared by cosonicating 3 + DODAB were found to increase curvilinearly to a plateau value, indicating domain formation. Subsequent to vesicle polymerization, cumulants, weight- and number-average molecular weights of the separated poly(vinylbenzoates) and, hence, the average chain lengths were determined by gel exclusion chromatography. The average chain lengths varied from 10 in laser-polymerized 3 vesicles, through 20 in laser-polymerized vesicles prepared from mixtures of DODAB and vinylbenzoic acid, to 40 in laser-polymerized vesicles prepared from mixtures of 3 and vinylbenzoic acid. These relatively small chain lengths were discussed in terms of the restricted geometries prevailing at intravasicular surface polymerizations. Fluorescence measurements and a Monte Carlo based computer simulation of the photopolymerization were used to substantiate the proposed mechanism of vesicle polymerization.