Cationic polymerization of a novel oxetane-bearing ionic liquid structure and properties of the obtained poly(ionic liquid)

Abstract

An ionic liquid, 1-ethyl-3-(3-ethyl-3-oxetanylmethyl)imidazolium bis(trifluoromethanesulfonyl)imide (OXImTFSI), was synthesized, and its cationic polymerization was examined. The heating of a mixture of 1-ethylimidazole and 3-chloromethyl-3-ethyloxetane at 90 °C for 48 h yielded 1-ethyl-3-(3-ethyl-3-oxetanylmethyl)imidazolium chloride, which was transformed to a roomerature ionic liquid, OXImTFSI, by ion exchange with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). This ionic liquid was polymerized using boron trifluoride ethyl ether complex as a catalyst to give polyOXImTFSI. Five percent weight loss temperature (T d5) of polyOXImTFSI evaluated by thermal gravimetric analysis was 409 °C, indicating the high thermal stability. Glass transition temperature (T g) of the polymer evaluated by differential scanning calorimetry was -19 °C, indicating the high flexibility of the material. Ionic conductivity of polyOXImTFSI was determined to be 1.86 × 10-8 S/cm at 23 °C, which was far lower than that of the OXImTFSI monomer (5.05 × 10-4 S/cm).