Polymerization of micelle-forming monomers: Mechanistic study and characterization of the systems before and after polymerization

Cationic surfactants bearing a polymerizable styryl headgroup and a variable alkyl chain with 8–16 carbon atoms have been synthesized. Their aqueous solutions have been characterized by the surfactant critical micellar concentration (CMC) and aggregation number using electrical conductivity, spectrofluorimetry and time-resolved fluorescence quenching. The photoinitiated polymerization of these surfactants in the micellar state led to stable and transparent or slightly bluish systems. The kinetics of polymerization were measured by dilatometry and were found to be close to those obtained for styrene emulsion polymerization. A mechanism of polymerization is proposed and discussed in terms of micellar dynamics. The polymerized systems, p(Cn-STY), and the recovered polymers were characterized by means of several complementary techniques. The polymers have high molecular weights (3 × 10⁵-3 × 10⁶), which indicates that the initial micellar structure is not preserved upon polymerization. The structure of the polymerized systems depends on the alkyl chain length of the surfactant. The p(C16-STY) systems exhibit a structure similar to that of a polysoap with intramolecular hydrophobic microdomains whereas the p(C8-STY) systems behave like classical polyelectrolytes.