Electrical characteristics of ion gels prepared by loading different amounts of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([EMIM][TFSI]) in Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) are investigated and compared with those of ion liquid, [EMIM][TFSI] for possible application as a gate stack for flexible electronic devices. Capacitance and impedance as a function of frequency are measured, which can be well accounted for by a simple circuit model identifying the local device components. The operation of a flexible field effect transistor based on graphene and the ion gel as a top gate stack is also demonstrated. (C) 2018 Korean Physical Society. Published by Elsevier B.V. All rights reserved.