Thermal analysis and ionic conductivity of ionic liquid containing composites with different crosslinkers

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Abstract

Conductive polymer composites were synthesized by the polymerization of methylmethacrylate in the presence of ionic liquid solvents. These composites were characterized by attenuated total reflectance infrared spectroscopy, differential scanning calorimetry, and dynamic mechanical analysis. AC impedance measurements were performed on these composites as a function of ionic liquid type, ionic liquid concentration, crosslinker density, and molecular weight between crosslinks at various temperatures. 1-Butyl-3-methylimidazolium thiocyanate produced composites with a greater conductivity than 1-ethyl-3-methylimidazolium trifluoromethanesulfonimide, despite having a higher viscosity. The viscosity of the virgin ionic liquid could not be used to predict the order of ionic conductivity for composites made from these ionic liquids. The effect of crosslink density within the range of 0–0.6 mmol crosslinking agent per gram of monomer was studied. Composites with 25% ionic liquid (w/w) appeared to have an optimum crosslink density for maximum ionic conductivity. In the range of crosslink densities studied, composites with greater ionic liquid concentration exhibited no significant effect of crosslink density on ionic conductivity. This could be due to the fact that the difference in crosslink density did not effectively change the Tg of these composites. The composite with the lowest theoretical molecular weight between crosslinks had the lowest ionic conductivity. This could be due to restriction of ion movement at this molecular weight between crosslinks. The composite with the highest molecular weight between crosslinks had comparable ionic conductivity to an uncrosslinked composite. This study showed that these materials have ionic conductivities practical for advanced energy applications over a wide range of morphologies with dimensional stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

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