Nanostructured proton-conducting membranes based on polymerizable zwitterionic ionic liquid microemulsions

Ionic liquid (IL)-microemulsions with a polymerizable zwitterionic IL as the polar core were successfully fabricated for the first time using a room temperature IL: 1-(3-sulfopropyl)-3-ethenyl-imidazolium methanesulfonate ([VIPS][MSA]), an anionic surfactant: 4-dodecyl benzenesulfonic acid and styrene. The IL-microemulsion phase diagram was determined. Nanostructured proton-conducting membranes were obtained using an in situ photopolymerization of the IL-microemulsion in different subregions. The Film-Bi obtained using a bicontinuous microemulsion exhibits a higher conductivity and lower activation energy than Film-O/IL or Film-IL/O. The macroscopically interconnected polar zwitterionic IL channels formed in bicontinuous microemulsions can work as proton pathways and supply more hopping sites for proton transportation. This simple and effective method provides a versatile format to prepare IL-based proton conductors.