Reversible-deactivation radical polymerization of chloroprene and the synthesis of novel polychloroprene-based block copolymers by the RAFT approach

Reversible addition-fragmentation chain transfer (RAFT) polymerization of the reactive monomer chloroprene (2-chloro-1,3-butadiene) mediated by ethyl 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate (EPDTB), 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPDTB) and dibenzyl trithiocarbonate (DBTTC) was investigated in benzene using 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. Polychloroprene (PCP) chains with predetermined molecular weights and low molar mass dispersities were synthesized by RAFT polymerization using EPDTB and CPDTB. The work described here also showed for the first time that well-defined polystyrene-block-polychloroprene (PSt-b-PCP) and poly(methyl methacrylate)-block-polychloroprene (PMMA-b-PCP) with controlled number averaged molecular weights and molecular weight distributions can be prepared in solution polymerization, employing EPDTB and 2-cyanoprop-2-yl dithiobenzoate (CPDB), respectively, as the initial RAFT agent. The success of the block copolymerization was showed by the shift toward higher molar mass of the size exclusion chromatography (SEC) chromatograms recorded before and after block copolymerization. Structural confirmation of the diblock copolymers was accomplished by H-1 NMR measurements. The results obtained from SEC analysis together with H-1 NMR spectroscopy demonstrate the possibility to design and prepare well-defined PCP-based block copolymers.