CHAIN TRANSFER BY ADDITION-FRAGMENTATION MECHANISM .9. ACCESS TO DIENE-FUNCTIONAL MACROMONOMERS USING 5-(SUBSTITUTED)-1,3-PENTADIENE-TYPE ADDITION-FRAGMENTATION CHAIN-TRANSFER AGENTS IN RADICAL POLYMERIZATION

Radical polymerizations of methyl methacrylate (MMA) and styrene (St) in bulk at low conversion were carried out in the presence of pentadie nic chain transfer agents ((CTA), 5-bromo-1,3-pentadiene (1), 5-benzen esulphonyl-1,3-pentadiene (2) and methyl 2-bromomethyl-4-methyl-2,4-pe ntadienoate (3), to produce conjugated diene-end capped macromonomers by a addition-fragmentation mechanism. The chain-transfer constants (C -tr) of 1, 2 and 3 for MMA polymerization were obtained from the Mayo equation, respectively. Correction to zero conversion afforded an accu rate value of the chain transfer constant for 1. The chain transfer wa s found to be degradative. The pentadienyl group formed by fragmentati on of the macroradical abduct is quantitatively introduced at the omeg a-end of the polymer. (C) 1997 Elsevier Science Ltd.