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

摘要

Radical polymerizations of methyl methacrylate (MMA) and styrene (St) in bulk at low conversion were carried out in the presence of pentadienic chain transfer agents ((CTA), 5-bromo-1,3-pentadiene (1), 5-benzenesulphonyl-1,3-pentadiene (2) and methyl 2-bromomethyl-4-methyl-2,4-pentadienoate (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 accurate value of the chain transfer constant for 1. The chain transfer was found to be degradative. The pentadienyl group formed by fragmentation of the macroradical abduct is quantitatively introduced at the omega-end of the polymer. (C) 1997 Elsevier Science Ltd.