Oh Sol Mi, Lee Victoria S, Drayer William F, Win Max S, Jones Lindsay F, Leo Courtney M, Kennemur Justin G, Frischknecht Amalie L, Winey Karen I
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
JACS Au. 2025 Jun 5;5(6):2641-2653. doi: 10.1021/jacsau.5c00218. eCollection 2025 Jun 23.
Using all-atom molecular dynamics simulations and a variety of experimental methods, we previously reported on a linear polyethylene with pendant phenyl sulfonated groups precisely on every fifth carbon along the backbone. With increasing relative humidity this fluorine-free polymer self-assembled to form nanoscale water channels and exhibited exceptional proton conductivity. Expanding upon those findings, here we explore partially sulfonated random copolymers, referred to as 5PhSH-. Using either acetyl sulfate or sulfuric acid, a wide range of sulfonation levels were prepared ( = 34-98%) corresponding to ion-exchange capacities (IEC) of 2.0-4.4 mmol/g. Combining experimental techniques and all-atom molecular dynamics simulations, we study the effect of on water uptake, nanoscale morphology, and the proton/water transport properties of 5PhSH-. The proton conductivity of 5PhSH- increases with relative humidity and with and achieves values in excess of 0.1 S/cm. These high conductivities are attributed to high IEC and well-developed nanoscale percolated hydrophilic domains made possible by the flexible backbone. We quantitatively describe the nature of the water channels using the characteristic distance, channel width distribution, the area per sulfonate group at the hydrophilic/hydrophobic interface, and the fractal dimension. Notably, the channel widths and the areas per sulfonate group are nominally independent of the level of sulfonation, while depending significantly on the level of hydration. The fractal dimension of the water channels correlates strongly with the water diffusion coefficients calculated from the molecular dynamics (MD) simulations. These findings demonstrate that the 5PhSH- hydrocarbon copolymers can be modified to tune properties, particularly proton conductivity.
我们之前利用全原子分子动力学模拟和多种实验方法，报道了一种线性聚乙烯，其侧链苯磺化基团精确地位于主链上每隔五个碳原子处。随着相对湿度的增加，这种无氟聚合物自组装形成纳米级水通道，并表现出优异的质子传导率。在此基础上，我们进一步研究了部分磺化的无规共聚物，即5PhSH-。使用乙酰硫酸或硫酸制备了一系列磺化水平（= 34 - 98%），对应离子交换容量（IEC）为2.0 - 4.4 mmol/g。结合实验技术和全原子分子动力学模拟，我们研究了磺化水平对5PhSH-的吸水率、纳米级形态以及质子/水传输性能的影响。5PhSH-的质子传导率随相对湿度和磺化水平的增加而提高，达到超过0.1 S/cm的值。这些高传导率归因于高IEC以及由柔性主链形成的发达的纳米级渗透亲水区域。我们使用特征距离、通道宽度分布、亲水/疏水界面处每个磺酸根基团的面积以及分形维数定量描述了水通道的性质。值得注意的是，通道宽度和每个磺酸根基团的面积名义上与磺化水平无关，而显著取决于水合水平。水通道的分形维数与通过分子动力学（MD）模拟计算得到的水扩散系数密切相关。这些发现表明，可以对5PhSH-碳氢共聚物进行改性以调节性能，特别是质子传导率。
