Ionic conduction of slide-ring gel swollen with ionic liquids

Abstract

The slide-ring (SR) gels derived from polyethylene glycol (PEG) threatened with polyrotaxane or hydroxypropyl polyrotaxane and crosslinked by 1,4-butanediol diglycidil ether were swollen with ionic liquids (ILs) and their ionic conduction was investigated. The molar conductivity of an SR gel swollen with 1-ethyl-3-methylimidazolium ethylsulfate (EMIES) with a high swelling ratio and with a small crosslinking density was more than 92% of that of neat IL. With increasing crosslinking density, the swelling ratio and molar conductivity decreased due to increasing disturbance of ion transport by the polymer networks, wherein the hydrodynamic radius of the ionic motion unit was estimated to be 9.7 nm from the relation between the mesh size of SR gels and conductivity. Further, the ionic conduction of SR gels swollen with ILs under compressive deformation was measured. With increasing compressive deformation, the ionic conductivity first increased to a peak at a compression ratio of about 0.75 and then subsequently decreased. This conductivity change can be explained by anisotropic deformation of SR gel networks under compressive deformation.