Novel star block copolymers containing poly(N-vinylimidazolium salt) as a poly(ionic liquid) segment and poly(N-isopropylacrylamide) (poly(NIPAAm)) as a thermoresponsive segment were synthesized by reversible additionfragmentation chain transfer (RAFT) polymerization. Two R-designed tetrafunctional chain transfer agents (CTAs), including a xanthate-type CTA and a dithiocarbamate-type CTA, were compared for the polymerization of 1-ethyl-3-vinylimidazolium bromide (VEI-Br), which is an ionic liquid-type monomer. The dithiocarbamate-type tetrafunctional CTA was the most efficient CTA for the controlled synthesis of four-armed poly(VEI-Br) stars with low polydispersity values and controlled molecular weights. Star block copolymers with inner thermoresponsive segments connected to their core were synthesized by the RAFT polymerization of VEI-Br, using poly(NIPAAm) stars. In contrast, the RAFT polymerization of NIPAAm using poly(VEI-Br) stars afforded star block copolymers, with block arms consisting of outer block copolymer segments of thermoresponsive poly(NIPAAm). Thermally induced phase separation behavior and assembled structures of star block copolymers were studied in aqueous solution. Keywords: block copolymer; micelle; poly(ionic liquid); self-assembly; star polymer; star block copolymer; thermoresponsive polymer INTRODUCTION Recently, considerable attention has been paid to polymerized ionic liquids or polymeric ionic liquids, which are macromolecules obtained from the polymerization of ionic liquid monomers. [1][2][3] Polymeric ionic liquids with unique and attractive properties can be obtained by adjusting the structure of the cation (for example, imidazolium, pyridinium and tetraalkylammonium) and the anion (for example, halide, tetrafluoroborate and hexafluorophosphate). Potential applications of polymeric ionic liquids include polymeric electrolytes, catalytic membranes, ionic conductive materials, CO 2 absorbents, microwave absorbents and porous materials. Imidazolium salt is the most popular cation introduced into polymer backbones. A variety of polymers containing imidazolium moieties on their side chains have been developed, including poly(meth)acrylate, 4-7 polystyrene 8,9 and poly(N-vinyl imidazolium) 10-13 derivatives. The majority of these poly(ionic liquid)s were prepared by conventional radical polymerization. In addition to the structure of the substituent on the imidazolium ring, the solubility and properties of poly(Nvinylimidazolium salt) depend on the structure of the counteranion.As a result of recent progress in controlled radical polymerization (also known as controlled or living radical polymerization or reversible deactivation radical polymerization), well-defined block copolymers containing imidazolium moieties have been synthesized. 14,15 For example, Waymouth et al. 16,17 demonstrated the

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