Because of their potential utility as electrolyte membranes in capacitive devices ranging from batteries and supercapacitors to fuel cells and actuators, interest in poly(ionic liquids), PILs, continues to increase. Advantages that may be garnered by virtue of the use of PILs include the realization of single-ion conducting systems in which only target ions are mobile, a greatly expanded use-temperature range, and, design latitude in fabrication of thin film devices and devices having non-planar geometries. Our studies have been focused on poly(ionic liquids) derived from 4-vinylimidazolium salts. As compared to 1-vinylimidazolium polymers, attachment at the 4(5)-position of the imidazole ring affords increased rotational and translational degrees of freedom for the imidazolium moiety that may result in greater free volume and greater ability for the imidazolium moiety to interact cooperatively in the transport of target ions. In this presentation, the synthesis of 1-butyl-2,3-dimethyl-4-vinylimidazolium triflate, its polymerization, and, ion exchange to yield a trio of polymer salts is described. The thermal characteristics of tetrasubstituted poly(4-vinylimidazolium salts) and corresponding trisubstituted poly(4-vinylimidazolium salts) were evaluated. While the mid-point glass transition temperatures, Tg-mid, for the trisubstituted 4-vinylimidazolium polymers with CF3SO3−, TFSI− and PF6− counterions were found to be 153 °C, 88 °C and 200 °C, respectively, the Tg-mid for the tetrasubstituted 4vinylimidazolium polymers with corresponding counter-ions was tightly clustered at 98 °C, 99 °C and 84 °C, respectively. This dramatically reduced influence of anion type on the glass transition temperature was attributed to the increased distance between the center of anions and cations in the poly(1-butyl-2,3-dimethyl-4-vinylimidazolium) polymer set.

Anomalous thermal characteristics of poly(ionic liquids) derived from 1-butyl-2,3-dimethyl-4-vinylimidazolium salts

249th National Meeting (2015)

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