Increased conductivity of polymerized ionic liquids through the use of a nonpolymerizable ionic liquid additive


In the present study, polymerizable ionic liquids (ILs), 1-[n-(methacryloyloxy)alkyl]-3-methylimidazolium bromides (n = 2, 6, 7, or 10), were synthesized in high yields. Moreover, the compounds obtained (n = 6, 7, or 10) were used in the preparation of composite materials comprising a polymerized IL matrix and a nonpolymerizable IL additive, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) in various proportions (up to 75% vol/vol of [EMIM][BF4]). The UV-radiation-initiated photopolymerization process was monitored in situ by measuring the resistivities of the mixtures. An increase in [EMIM][BF4] content in the composites led to an increase in the ionic conductivities of the materials while retaining their solid state at levels as high as 40% vol/vol of the [EMIM][BF4] content. The 40% vol/vol composites had conductivities of approximately 10−4 S/cm compared to the conductivities of 10−5 S/cm for the corresponding neat polymerized ILs. Above this [EMIM][BF4] content, the materials were sticky gels, and from 50% vol/vol onwards, entirely liquid.

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The authors would like to acknowledge the Estonian Science Foundation (Grant Nos. 8428 and 8794), Estonian Ministry of Education and Research (targeted Grant No. SF0180058s07), the European Regional Development Fund (Center of Excellence, Mesosystems: Theory and Applications, TK114; and “TRIBOFILM” 3.2.1101.12-0028), and the graduate school “Functional materials and technologies,” which received funding from the European Social Fund under Grant No. 1.2.0401.09-0079 in Estonia. The authors would like to acknowledge the NordForsk (Excellent Nordic Chemistry) for support. The authors also thank Silver Leinberg for his help with resistivity measurements.

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Põhako-Esko, K., Timusk, M., Saal, K. et al. Increased conductivity of polymerized ionic liquids through the use of a nonpolymerizable ionic liquid additive. Journal of Materials Research 28, 3086–3093 (2013).

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