Alkyl‐Substituted N ‐Vinylimidazolium Polymerized Ionic Liquids: Thermal Properties and Ionic Conductivities

Structure‐property relationships for polymerized ionic liquids (PILs) relate chemical structure to ionic conductivity and reveal the importance of glass transition temperature ( T g ) 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, T D , increases. As the length of the alkyl substituent increases, T g decreases for PILs with Br − and BF 4 − counteranions. Ionic conductivity increases over an order of magnitude upon exchange of the counteranion from TfO − < Tf 2 N − .