Synthesis of Comb Polymers via Grafting-Onto Macromolecules Bearing Pendant Diene Groups via the Hetero-Diels-Alder-RAFT Click Concept

Comb polymers were synthesized by the grafting-onto method via a combination of Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and the hetero-Diels-Alder (HDA) cycloaddition. The HDA reactive monomer trans, trans-hexa-2,4-dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Cross linking 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 pyridin-2-yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 degrees 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 stoichiometry. 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. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 4.8: 1773-1781, 2010