화학공학소재연구정보센터
Polymer, Vol.55, No.8, 1920-1930, 2014
Synthesis of thermoresponsive block and graft copolymers via the combination of living cationic polymerization and RAFT polymerization using a vinyl ether-type RAFT agent
A novel vinyl ether-type RAFT agent, benzyl 2-(vinyloxy)ethyl carbonotrithioate (BVCT) was synthesized for various block copolymers via the combination of living cationic polymerization of vinyl ethers and reversible addition fragmentation chain transfer (RAFT) polymerization. The novel BVCT trifluoroacetic acid adduct play an important role to produce well-defined block copolymers, which is both as a cationogen under EtA1C1(2) initiation system in the presence of ethyl acetate for living cationic polymerization and a RAFT agent for blocks by RAFT polymerization. The resulting polymer, poly(vinyl ether)s, by living cationic polymerization had a high number average alpha-end functionality (>= 0.9) as determined by both H-1 NMR and MALDI-TOF-MS spectrometry. In addition, this poly(vinyl ether)s worked well as a macromolecular chain transfer ageni for RAFT polymerization. The RAFT polymerization of radically polymerizable monomers was conducted in toluene using 2,2'-azobis(isobutyronitrile) at 70 C. For example, a double thermoresponsive block copolymer (MOVE61-b-N1PAM(150)) consisting of 2-methoxyethyl vinyl ether (MOVE) and N-isopropylacrylamide (NIPAM) was prepared via the combination of living cationic polymerization and RAFT polymerization. The block copolymer reversibly formed and deformed micellar assemblies above the phase separation temperature (T-ps) of poly(NIPAM) block in water. This BVCT is not only functioned as an initiator, but also acted as a monomer. When BVCT was copolymerized with MOVE by living cationic polymerization, followed by graft copolymerization with NIPAM via RAFT polymerization, well-defined graft copolymers (MOVEn-co-BVCTt(m))-g-NIPAM(x) (n = 62-73, m = 1-9, x = 19-214) were successfully obtained. However, no micelle formed in water above T-ps of poly(NIPAM) graft chain unlike the case of block copolymers. (c) 2014 Elsevier Ltd. All rights reserved.