Mechanical behavior of poly(methyl methacrylate)-based ionogels

Ionogels are formed when a cross-linked polymer network absorbs an ionic liquid. Ionogels are ionic conductors and, as such, are being considered for use in stretchable electronics and artificial muscles or nerves. The use of ionogels in these applications is limited in part by their mechanical behavior. Here we present an ionogel prepared by swelling covalently cross-linked poly(methyl methacrylate) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The resulting ionogel is compliant, stretchable, and relatively tough. We demonstrate that the swelling ratio, elastic modulus, stretchability, and fracture energy of the ionogel depend sensitively on the cross-link density of the polymer network. The behavior of the ionogel is well captured by the model of the ideal elastomeric gel combined with the Flory-Huggins model for the energy of mixing.