GREMAN, CNRS UMR 7347, Université de Tours, 37200 Tours, France.
Department of Energy Science and Engineering, DGIST, Daegu 42988, Korea.
J Phys Chem B. 2021 Feb 25;125(7):1916-1923. doi: 10.1021/acs.jpcb.0c10068. Epub 2021 Feb 15.
Water solubility of PEDOT:PSS conducting polymer is achieved by PSS at the expense of disturbing the crystallinity and electron mobility of PEDOT. Recently, PEDOT crystallinity and electron mobility have been improved by treating the PEDOT:PSS aqueous solution with 1-ethyl-3-methylimidazolium- (EMIM-) based ionic liquids (IL) EMIM:X. The amount of such improvement varies drastically with the anion X coupled to EMIM cation in the IL. Herein, using umbrella-sampling molecular dynamics simulations on the aqueous solutions of a minimal model of PEDOT:PSS mixed with various EMIM:X ILs, we show that the solvation of each ion in water plays a major role in the free energies of ion binding and exchange. Anions X efficient for the improvement are weakly stabilized by hydration (i.e., hydrophobic) and prefer binding to hydrophobic PEDOT than to hydrophilic EMIM, favoring the ion exchange. In order to fulfill our design principle, a quantitative criterion based on hydration free energy is proposed to select efficient hydrophobic anions X.
PSS 导电聚合物的水溶性是通过 PSS 实现的，这会损害 PEDOT 的结晶度和电子迁移率。最近，通过用 1-乙基-3-甲基咪唑鎓（EMIM-）基离子液体（IL）EMIM:X 处理 PEDOT:PSS 水溶液，改善了 PEDOT 的结晶度和电子迁移率。这种改善的程度与 IL 中与 EMIM 阳离子结合的阴离子 X 有很大的不同。在此，我们使用伞形采样分子动力学模拟研究了与各种 EMIM:X IL 混合的 PEDOT:PSS 最小模型水溶液，结果表明，每种离子在水中的溶剂化作用在离子结合和交换的自由能中起着主要作用。有利于改善的阴离子 X 通过水合作用（即疏水性）得到弱稳定，并优先与疏水性 PEDOT 结合，而不是与亲水性 EMIM 结合，有利于离子交换。为了满足我们的设计原则，提出了一个基于水合自由能的定量标准，用于选择有效的疏水性阴离子 X。
