RAFT Polymerization of N-Vinylimidazolium Salts and Synthesis of Thermoresponsive Ionic Liquid Block Copolymers

The polymerizations of N-vinylimidazolium salts, 1-(3-phynylpropyl)-3-vinylimidazolium bromide (PVI-Bt). 1-(6-ethoxycarbonylhexyl)-3-vinylimidazolium bromide (EHV1-Br), and 1-(2-ethoxyethyl)-3-vinylimidazolium bromide (EtoEVI-Br), were performed by reversible addition-fragmentation chain transfer (RAFT)/macromolecular design via interchange of xanthate (MADIX) process Two xanthate-type chain transfer agents (CTAs), O-ethyl-S-(1-phenylethyl) dithiocarbonate (CTA 1) and O-ethyl-S-(1-ethoxycarbonyl) ethyldithiocarbonate (CTA 2), proved efficient for obtaining poly(PVI-Br)s and (EHVI-Br)s with relatively low polydispersities (M-w/M-n < 1 4) Poly(EtOEVI-Bi)s with moderate molecular weight distributions (M-w/M-n = 1.5-1.6) were also obtained under the same conditions. Controlled character of the polymerization of PVI-Br was confirmed by the molecular weight controlled by the monomer/CTA molar ratio, a linear increase in the number-average molecular weight (M-n) with conversion, and the ability to extend the chain by a second addition of monomer Polymerizations of the N-vinylimidazolium salts using the dithrocarbonate-terminated poly(N- isopropylacrylamide) as a macro-chain-transfer agent provided well-defined thermoresponsive ionic liquid block copolymers, Thermally induced phase separation behavior and assembled structures of the block copolymers were also studied in aqueous solution.