An upper critical solution temperature (UCST)type phase separation in water was achieved using well-defined polymeric ionic liquids (ILs) with imidazolyl groups in their side chains, prepared based on living cationic polymerization using a cationogen/Et 1.5 AlCl 1.5 initiating system with 1,4-dioxane as an added base. Aqueous solutions of the polymers with tetrafluoroborate as counteranions showed sharp and reversible UCST-type phase separation at 5−15 °C. The effect of polymer concentration, chain-end groups, and molecular weight on the phase separation temperature suggests that the phase separation resulted from interpolymer electrostatic interactions. Other polymeric ILs with SbF 6− also showed a lower critical solution temperature-type phase separation in various organic solvents.

Novel dual thermosensitive diblock copolymers with an imidazolium salt and oxyethylene side-chains which self-assemble into micelles and vesicles in water depending on the temperature are precisely synthesized.

Controlled cationic polymerization of isobutyl vinyl ether was demonstrated to proceed in an ionic liquid (IL), 1butyl-3-octylimidazolium bis(trifluoromethanesulfonyl)imide, using a 1-(isobutoxy)ethyl acetate/TiCl 4 initiating system, ethyl acetate as an added base, and 2,6-di-tert-butylpyridine as a proton trap reagent. Judicious choices of metal halide catalysts, counteranions of ILs, and additives were essential for controlling the polymerization. The polymerization proceeded much faster in the IL than in CH 2 Cl 2 , indicating an increased population of ionic active species in the IL due to the high polarity.Polymers with a relatively narrow molecular weight distribution were obtained in the IL with a bis(trifluoromethanesulfonyl)imide (NTf -2 ) anion even in the absence of an added base, which suggested possible interactions of the counteranion of the IL with the growing carbocations. Moreover, the direct cationic polymerization of a vinyl ether with pendant imidazolium salts, 1-(2-vinyloxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, proceeded in a homogeneous state in 1methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)imide. The solubilities of the obtained polymers were readily tuned by counteranion exchange.