UV polymerization of room temperature ionic liquids for high temperature PEMs: Study of ionic moieties and crosslinking effects

The conductivity performance of commercial available room-temperature ionic liquids (RTILs) has been evaluated from room conditions up to 200 °C as a function of relative humidity for their potential application in high temperature PEMs. In particular, ammonium and imidazolium based ionic liquids with different counterions and substituents have been investigated. On the basis of conductivity performance, the best RTILs have been selected for the preparation of all solid state ion conductive films by bulk photo-assisted radical polymerization. The goodness of the UV photopolymerization of the respective monomeric ionic liquids (MILs) with vinyl functionality as a function of divinylbenzene cross-linker content has been evaluated by TGA and FTIR analyses. Poly-ionic liquid (PIL) films have been successfully accomplished for polymerized H-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide upon exposure to 365 nm UV lamp with an intensity of 2.4 mW/cm2 for 15 min. Conductivity values above 1.1 S cm−1 at 200 °C have been registered for pure poly[1-(3H-imidazolium)ethylene] bis(trifluoromethanesulfonyl)imide.