Synthesis of arborescent styrene homopolymers and copolymers from epoxidized substrates

The synthesis of arborescent styrenic homopolymers and copolymers was achieved by anionic polymerization and grafting. Styrene and p-(3-butenyl)styrene were first copolymerized using sec-butyllithium in toluene, to generate a linear copolymer with a weight-average molecular weight Mw = 4000 and Mw/Mn = 1.05. The pendant double bonds of the copolymer were then epoxidized with m-chloroperbenzoic acid. A comb-branched (or arborescent generation G0) copolymer was obtained by coupling the epoxidized substrate with living styrene-p-(3-butenyl)styrene copolymer chains with Mw similar to 5000 in a toluene/tetrahydrofuran mixture. Further cycles of epoxidation and coupling reactions while maintaining Mw similar to 5000 for the side chains yielded arborescent copolymers of generations G1G3. A series of arborescent styrene homopolymers was also obtained by grafting Mw similar to 5000 polystyrene side chains onto the linear and G0G2 copolymer substrates. Size exclusion chromatography measurements showed that the graft polymers have low polydispersity indices (Mw/Mn = 1.021.15) and molecular weights increasing geometrically over successive generations. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012