Morphology, Modulus, and Conductivity of a Triblock Terpolymer/Ionic Liquid Electrolyte Membrane

详细信息    查看全文

• 作者：Lucas D. McIntosh ; Tomohiro Kubo ; Timothy P. Lodge
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：February 11, 2014
• 年：2014
• 卷：47
• 期：3
• 页码：1090-1098
• 全文大小：524K
• ISSN：1520-5835

文摘

Block polymers are ideally suited for polymer electrolytes exhibiting both high ionic conductivity and superior mechanical robustness because they self-assemble into well-defined nanostructures. Network morphologies exhibiting long-range continuity of both the mechanically robust and conductive domains maximize the macroscopic composite properties but are difficult to achieve in commonly studied diblock copolymer systems. We therefore investigated a polymer electrolyte comprising the triblock terpolymer poly[isoprene-b-(styrene-co-norbornenylethylstyrene)-b-ethylene oxide] (INSO) and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) because INSO self-assembles into equilibrium network morphologies in which each domain is continuous throughout the sample. Small-angle X-ray scattering and transmission electron microscopy revealed the bulk morphology of INSO to be the O⁷⁰ network prior to cross-linking. The material remained microphase-separated but without long-range order after solvent-casting from dichloromethane, a morphology that was retained after cross-linking and the addition of ionic liquid. Cross-linking had the effect of increasing the elastic modulus by 4 orders of magnitude, from 10⁴ to 10⁸ Pa, and importantly, a high modulus was retained well above the T_g of linear polystyrene. The conductivity was somewhat lower than that expected for a heterogeneous electrolyte, but the results suggest that refinements to the solvent-casting procedure could increase connectivity of the conductive domain and thus macroscopic conductivity.