Star-polymer synthesis via radical reversible addition-fragmentation chain-transfer polymerization

Polystyrene stars were synthesized by reversible addition-fragmentation cha in-transfer (RAFT) polymerization using hexakis(thiobenzoylthiomethyl)benze ne (I) as a hexafunctional RAFT agent at 80, 100, and 120 degreesC. The pol ymerizations conformed to pseudo-first-order kinetic behavior. TI-ie molecu lar weight distributions displayed characteristics consistent with a living radical process. A number of salient features were observed in the molecul ar weight distributions with the star distribution accompanied by a linear polymer-chain distribution and shoulders on the distributions that can be a ttributed to radical-radical-termination events. The evidence suggests that high temperatures are required to activate all the RAFT active sites on I, and a hypothesis proposes that there is significant steric hindrance in th e initial stages of the RAFT process with I. (C) 2001 John Wiley & Sons, In c.