Star polymer synthesis using trithiocarbonate functional β-cyclodextrin cores (Reversible addition-fragmentation chain-transfer polymerization)

Polystyrene stars were synthesized with reversible addition-fragmentation chain-transfer (RAFT) polymerization. The core of the stars comprised a trithiocarbonate heptafunctional beta-cyclodextrin ring. Polymerizations were performed at 100 and 120 degreesC in the absence of an extraneous initiator and at 60 degreesC in the presence of a radical initiator. Monofunctional trithiocarbonate was also synthesized and used to make linear polystyrene to allow direct a comparison with the star synthesis. In all cases, the polymerization kinetics conformed to pseudo-first-order behavior. The measured molecular weights of the stars were found to deviate from those predicted on the basis of the monomer/trithiocarbonate group ratio. The extent of this deviation was dependent on the polymerization temperature, RAFT agent concentration, and conversion. Despite the low radical concentrations, termination reactions are suggested to play a significant role in the seven-arm polystyrene star syntheses. The synthetic method was found to be suitable for generating star block structures. (C) 2002 Wiley Periodicals, Inc.