Pulsed-laser polymerization in compartmentalized liquids. 1. Polymerization in vesicles

Polymerization in vesicles is a novel type of polymerization in heterogeneo us media, leading to parachute-like vesicle-polymer hybrid morphologies. To explore the kinetics of vesicle polymerizations and to learn more about th e actual locus of polymerization we applied the pulsed-laser polymerization (PLP) technique to the polymerization of styrene in small and large unilam ellar dioctadecyldimethyl-ammonium bromide (DODAB) vesicles. The analysis o f the molecular weight distribution (MWD) allows primarily the determinatio n of the monomer concentration at the site of polymerization if the propaga tion rate coefficient, k(p), of the applied monomer is known. Relatively hi gh monomer concentrations (between 2.6 and 4.5 mol/L) were found at the loc us of polymerization at low conversions. PLP experiments as a function of o verall monomer concentration, temperature, and vesicle size gave insight in to the monomer partitioning between vesicle and polymerization site. With r espect to the mechanism of polymerization in vesicles, the observations see m to indicate that polymerization occurs iii a small polymer nucleus where high monomer concentrations are encountered.