Synthesis of comb polymers via grafting-onto macromoleeules bearing pendant diene groups via the hetero-diels-alder-raft click concept
Résumé
Comb polymers were synthesized by the "graftingonto" method via a combination of Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and the hetero-DielsAlder (HDA) cycloaddition. The HDA reactive monomer trans, transhexa-2,4-dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Crosslinking was minimized by decreasing the monomer concentration-whilst keeping monomer to polymer conversions low-resulting in reactive backbones with on average one reactive pendant diene groups for 10 styrene units. The HDA cycloaddition was performed between the diene functions of the copolymer and a poly(n-butyl acrylate) (PnBA) prepared via RAFT polymerization with pyridîn-2-yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 °C and the grafting yield varies from 75% to 100%, depending on the number average molecular weight of the PnBA (3500 g mol-1 < Mn < 13,000 g mol-1) grafted chain and the reaction stoiehiometry. The molecular weights of the grafted block copolymers range from 19,000 g mol -1 to 58,000 g mol-1 with polydispersities close to 1.25. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A:.