KINETICS OF ARM-FIRST STAR POLYMERS FORMATION IN A NONPOLAR SOLVENT

Star polymer formation by sequential anionic copolymerization of styre ne and divinylbenzene in a non-polar solvent (benzene) was re-examined . Kinetic investigations established that the core formation is rather slow. Moreover, once the star molecules have reached their plateau mo lar mass, their cores still contain residual pendant unsaturations. Th is result arose from UV spectroscopic determinations, and was checked by sec-butyllithium addition to the star polymer solution. Fractionati on experiments confirmed the rather narrow molar mass distribution in star polymer samples obtained by this arm-first process.