Alkyl-substituted N-vinylimidazolium polymerized ionic liquids: Thermal properties and ionic conductivities

Abstract

Structure-property relationships for polymerized ionic liquids (PILs) relate chemical structure to ionic conductivity and reveal the importance of glass transition temperature (Tg) and the energy associated with an ion-hopping mechanism for ion conduction for a series of alkyl-substituted vinylimidazolium PILs. The alkyl-substituted vinylimidazolium-based PILs with varying lengths of n-alkyl substituents provide diverse precursors with exchangeable anions to further enhance thermal stability and ionic conductivity. As the anion size increases, regardless of alkyl substituent length, T g decreases and the onset of weight loss, TD, increases. As the length of the alkyl substituent increases, Tg decreases for PILs with Br- and BF4- counteranions. Ionic conductivity increases over an order of magnitude upon exchange of the counteranion from TfO- < Tf2N-. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.