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Preparation of Supramolecular Ionic Liquid Gels Based on Host–Guest Interactions and Their Swelling and Ionic Conductive Properties

Sinawang, Garry, Kobayashi, Yuichiro, Zheng, Yongtai, Takashima, Yoshinori, Harada, Akira, Yamaguchi, Hiroyasu
Macromolecules 2019 v.52 no.8 pp. 2932-2938
composite polymers, copolymerization, crosslinking, electrochemistry, gamma-cyclodextrin, gels, ionic liquids
Ionic liquid gels (IGs) have received much attention due to their electrochemical properties. IGs previously reported were formed by chemically cross-linked structures. The ionic conductivity (σ) of chemically cross-linked IGs was one order of magnitude lower than that of the native ionic liquid. Supramolecular polymeric IGs based on noncovalent bond cross-linkers have the potential to realize higher σ values. We prepared supramolecular polymeric IGs based on host–guest interactions. The supramolecular polymeric IG was prepared from bulk copolymerization of the host–guest complex between peracetylated γ-cyclodextrin (PAcγCD) and 2-ethyl-2-adamantane (Ad) in the presence of acrylate followed by immersing the copolymer in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIm TFSI). The σ value of the supramolecular polymeric IG was higher than those of the chemically cross-linked IGs. Although the σ values of the chemically cross-linked IG, Ad with chemically cross-linked IG, and PAcγCD with chemically cross-linked IG based on poly(ethyl acrylate) showed low σ values (0.54, 0.50, and 1.6 mS/cm, respectively), the σ value of the supramolecular polymeric IG based on poly(ethyl acrylate) reached 8 mS/cm, which is comparable to that of EMIm TFSI (9 mS/cm). These results indicated that the host–guest interaction in the supramolecular polymeric IG increases the σ value.