Comonomer effects on co-permeation of methanol and acetate in cation exchange membranes
Comonomer effects on co-permeation of methanol and acetate in cation exchange membranes
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DOI：
10.1016/j.eurpolymj.2021.110307
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发表时间：
2021-02-08
影响因子：
6
通讯作者：
Beckingham, Bryan S.
中科院分区：
文献类型：
--
作者：
Kim, Jung Min;Beckingham, Bryan S.
水合致密聚合物膜中的共渗透对于从能量转换（即光电化学二氧化碳还原电池）到液体分离（即全蒸发）的许多应用至关重要，在这些应用中，此类膜面临着复杂的物质混合物的挑战。例如，实现高效二氧化碳还原电池的一个主要挑战是设计具有足够电导率和二氧化碳还原产物（例如甲醇和乙酸盐）渗透最小的离子交换膜，因此需要了解这些溶质在离子交换膜中的渗透和共渗透行为。此前，研究了Nafion (R) 117和由聚乙二醇二丙烯酸酯（PEGDA，交联剂）和2-丙烯酰胺-2-甲基-1-丙磺酸（AMPS，磺化共聚单体）制备的交联阳离子交换膜对甲醇和乙酸钠的传输行为，并在与甲醇共渗透时观察到这些膜对乙酸钠的渗透性的明显变化。为了进一步研究这种共渗透行为，我们通过改变三种不同共聚单体的带负电荷的 AMPS 含量来修改 PEGDA-AMPS 结构：丙烯酸（AA，n = 0）、甲基丙烯酸 2-羟乙酯（HEMA，n = 1）和聚（乙二醇）甲基丙烯酸酯（PEGMA，n = 5），其中 n 代表每个共聚单体中环氧乙烷重复单元的数量。虽然观察到的具有短侧基共聚单体（PEGDA-AMPS/AA 和 PEGDA-AMPS/HEMA）的膜在与甲醇共渗透中对乙酸钠的渗透性有所增加，但对于 PEGDA-AMPS/PEGMA 膜而言，其相对一致。虽然这种行为的根本原因尚未解决，但我们根据我们的实验提出了甲醇辅助运输和环氧乙烷重复单元悬垂静电相互作用破坏相结合的方法。总体而言，这种传输行为的差异强调需要加强对水合致密聚合物膜中的紧急共渗透行为的理解。
Co-permeation in hydrated, dense polymer membranes is crucial to many applications from energy conversion (i. e. photoelectrochemical CO2 reduction cells) to liquid separation (i.e. pervaporation), where such membranes are challenged with complex mixtures of species. For instance, a major challenge to the realization of efficient CO2 reduction cells is the design of ion exchange membranes with sufficient conductivity and minimal permeation of CO2 reduction products (e.g. methanol and acetate), such that understanding permeation and copermeation behavior of these solutes in ion exchange membranes is needed. Previously, the transport behavior of Nafion (R) 117 and crosslinked cation exchange membranes prepared with poly(ethylene glycol) diacrylate (PEGDA, crosslinker) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS, sulfonated comonomer) to methanol and sodium acetate was investigated and distinct changes in permeabilities of these membranes to sodium acetate was observed in co-permeation with methanol. To further investigate this copermeation behavior, we modify the PEGDA-AMPS structure by varying the negatively-charged AMPS content with three different comonomers, acrylic acid (AA, n = 0), 2-hydroxylethyl methacrylate (HEMA, n = 1), and poly(ethylene glycol) methacrylate (PEGMA, n = 5), where n represents the number of ethylene oxide repeat units in each comonomer. While the observed permeability to sodium acetate in co-permeation with methanol was increased for membranes with comonomers with short pendant groups (PEGDA-AMPS/AA and PEGDA-AMPS/HEMA), it remained relatively consistent for PEGDA-AMPS/PEGMA membranes. While the underlying causes of this type of behavior remains unresolved, we propose a combination of assisted transport by methanol and disruption of electrostatic interactions by pendant ethylene oxide repeat units based on our experiments. Overall, such differences in transport behavior underscore the need for increased understanding of emergent copermeation behavior in hydrated, dense polymer membranes.