Gel–Polymer Electrolytes Based on Poly(Ionic Liquid)/Ionic Liquid Networks

The use of electrically charged, polymerized ionic liquids (polyILs) offers opportunities for the development of gel–polymer electrolytes (GPEs), but the rational design of such systems is in its infancy. In this work, we compare the properties of polyIL/IL GPEs based on 1-butyl-3-(4-vinylbenzyl)imidazolium bis(trifluromethanesulfonyl)imide containing trapped ammonium-based protic ionic liquids (ILs) with an analogous series based on the electrically neutral host polymer 1-(4-vinylbenzyl)imidazole. The materials are synthesized by photopolymerizing ionic and neutral monomers in the presence of diethylmethylammonium trifluoromethanesulfonate, [dema][TfO], diethylmethylammonium trifluoroacetate, [dema][TFAc], and diethylmethylammonium bis[trifluoromethanesulfonyl]imide, [dema][Tf2N], respectively. The resulting materials are characterized using electron microscopy, infrared spectroscopy, thermal analysis, Raman spectroscopy, and AC-impedance analysis. Spectroscopic analysis confirms that the ILs are distributed throughout the polymers, unless the GPE also contains poly(diallyldimethylammonium) bis[trifluoromethanesulfonyl]imide, when separation of the components occurs. The polyIL/IL GPEs are more electrochemically and thermally stable, and up to six times more conductive, than the materials based on the neutral host. As a proof-of-concept demonstration, we show that polyIL/IL gels can be 3D printed using readily available 3D-printing hardware.