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Thermal and ion transport properties of hydrophilic and hydrophobic polymerized styrenic imidazolium ionic liquids

Authors

  • Ryan L. Weber,

    1. Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave., Madison, Wisconsin 53706
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  • Yuesheng Ye,

    1. Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104
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  • Steven M. Banik,

    1. Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave., Madison, Wisconsin 53706
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  • Yossef A. Elabd,

    Corresponding author
    1. Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104
    • Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave., Madison, Wisconsin 53706
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  • Michael A. Hickner,

    Corresponding author
    1. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
    • Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104
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  • Mahesh K. Mahanthappa

    Corresponding author
    1. Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave., Madison, Wisconsin 53706
    • Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802
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Abstract

Polymerized ionic liquids (PILs) are a platform for fundamental studies of structure-property relationships in single ion conductors, with potential applications in energy storage and conversion. The synthesis, thermal properties, and ionic conductivities of homologous, narrow dispersity styrenic PILs are described. Hydrophilic poly(4-vinylbenzyl alkylimidazolium chloride) (PVBn(alkyl)ImCl) homopolymers with constant average degrees of polymerization were synthesized by post-synthetic functionalization of a poly(4-vinylbenzyl chloride) (Mn = 15.9 kg/mol, Mw/Mn = 1.34) master batch with N-alkylimidazoles (alkyl = [BOND]CH3 (Me), [BOND]C4H9 (Bu), and [BOND]C6H13 (Hex)). The chloride counterions of PVBnHexImCl were exhaustively metathesized with BFmath image, PFmath image, and bis(trifluoromethanesulfonyl)imide (TFSI) to yield a series of hydrophobic PILs. Thermogravimetric analyses indicate that PVBn(alkyl)ImCl homopolymers are unstable above 220 °C, whereas the hydrophobic PILs remain stable up to 290 °C. The glass transition temperatures (Tg) decrease with both increasing alkyl side-chain length and increasing counterion size, exemplified by Tg = 9 °C for PVBnHexImTFSI. Hydrophilic PILs exhibit high ionic conductivities (as high as ∼0.10 S cm−1) that depend on the relative humidity, water uptake, and the PIL side chain length. The hydrophobic PILs exhibit lower conductivities (up to ∼5 × 10−4 S cm−1) that depend predominantly on the polymer Tg, however, counterion size and symmetry also contribute. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1287–1296, 2011

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