Cycloalkenyl-functionalized polymers and block copolymers: Syntheses via selective raft polymerizations and demonstration of their versatile reactivity

A facile synthetic strategy for the preparation of well-defined polymers bearing cycloalkenyl side groups has been established via selective reversible addition fragmentation chain transfer (RAFT) polymerization of cycloalkene-functionalized asymmetrical divinyl monomers. Two representative monomers, 4-(6-methylcy-clohex-3-enylmethoxy)-2,3,5,6-tetrauorostyrene and 4-(cyclohex-3-enylmethoxy)-2,3,5,6-tetrauorostyrene, were synthesized. RAFT polymerizations of these bifunctional monomers, using S-1-dodecyl-S-(, -dimethyl- acetic acid)trithiocarbonate as the chain transfer agent and 2,2-azobis(isobutyronitrile) (AIBN) as the thermal initiator, exhibited superb selectivity toward the substituted styrenyl vinylic unit relative to the cyclohexenyl unit, even at high monomer conversions (80%). The resulting polymers retained quantitative cyclohexenyl groups, while having predetermined molecular weights and narrow molecular weight distributions (PDI 1.09 1.15). Well-defined block copolymers with pendent cyclohexenyl groups were also prepared by sequential RAFT chain extension polymerizations. A variety of functional polymers were further obtained by functional group transformations using the cyclohexene-functionalized polymers as precursors.