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Unraveling Depth-Specific Ionic Conduction and Stiffness Behavior across Ionomer Thin Films and Bulk Membranes
ACS Macro Letters ( IF 5.1 ) Pub Date : 2021-06-10 , DOI: 10.1021/acsmacrolett.1c00110
Seefat Farzin 1 , Ehsan Zamani 1 , Shudipto K Dishari 1
Affiliation  

Interfacial behavior of submicron thick polymer films critically controls the performance of electrochemical devices. We developed a robust, everyday-accessible, fluorescence confocal laser scanning microscopy (CLSM)-based strategy that can probe the distribution of mobility, ion conduction, and other properties across ionomer samples. When fluorescent photoacid probe 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) was incorporated into <1 μm thick Nafion films on substrates, the depth-profile images showed thickness- and interface-dependent proton conduction behavior. In these films, proton conduction was weak over a region next to substrate interface, then gradually increased until air interface at 88% RH. Conversely, consistently high proton conduction with no interface dependence was observed across 35–50 μm thick bulk, free-standing Nafion membranes. A hump-like mobility/stiffness distribution was observed across Nafion films containing mobility-sensitive probe (9-(2-carboxy-2-cyanovinyl)julolidine) (CCVJ). The proton conduction and mobility distribution were rationalized as a combinatorial effect of interfacial interaction, ionomer chain orientation, chain density, and ionic domain characteristics.

中文翻译:

揭示离子聚合物薄膜和体膜中特定深度的离子传导和刚度行为

亚微米厚聚合物薄膜的界面行为关键地控制着电化学装置的性能。我们开发了一种基于荧光共聚焦激光扫描显微镜 (CLSM) 的强大、日常可访问的策略,可以探测离子交联聚合物样品的迁移率、离子传导和其他特性的分布。当荧光光酸探针 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) 结合到基板上 <1 μm 厚的 Nafion 薄膜中时,深度剖面图像显示出与厚度和界面相关的质子传导行为。在这些薄膜中,质子传导在靠近基板界面的区域上很弱,然后逐渐增加,直到空气界面处于 88% RH。相反,在 35-50 μm 厚的块体上观察到一致的高质子传导,没有界面依赖性,独立式 Nafion 膜。在含有流动性敏感探针 (9-(2-carboxy-2-cyanovinyl) julolide) (CCVJ) 的 Nafion 薄膜中观察到了类似驼峰的流动性/刚度分布。质子传导和迁移率分布被合理化为界面相互作用、离聚物链取向、链密度和离子域特征的组合效应。
更新日期:2021-07-20
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