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Enhanced electrochemical response of solution-deposited n-doping polymer via cocasting with ionic liquid



A novel cocasting approach is presented for improving electroactivity of solution-cast films of conducting polymers. Solutions of the n-doping polymer poly(benzimidazobenzophenanthroline) (BBL) were co-deposited with the ionic liquid electrolyte 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMIBTI). The resultant co-continuous mixture yielded highly porous polymer films (CC-BBL) upon removal of solvent and EMIBTI. Electrochemical quartz crystal microgravimetry revealed that the n-doping process in neat ionic liquid is anion-dominant, which is contrary to what is observed in dilute electrolyte solutions. The CC-BBL films exhibit a thirty-fold increase in initial current response and capacity relative to non-cocast BBL films. While current response and capacity of the non-cocast BBL improve with cycling, they level out after 800 cycles at 35% of those of the CC-BBL. CC-BBL shows high n-doping stability; no decrease in electroactivity is seen after 1000 cycles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012