Absence of Schroeder's paradox: Experimental evidence for water-swollen Nafion membranes
Absence of Schroeder's paradox: Experimental evidence for water-swollen Nafion membranes
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DOI：
10.1016/j.memsci.2011.02.036
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发表时间：
2011-05
期刊：
影响因子：
--
通讯作者：
S. Jeck;P. Scharfer;M. Kind
中科院分区：
文献类型：
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作者：
S. Jeck;P. Scharfer;M. Kind
可以通过使聚合物样品与液体或气体溶剂平衡来分析聚合物膜中的溶剂吸附。然而，对于一些聚合物/溶剂系统，在饱和点处的测量已经揭示了从液体与相应的蒸气相的溶剂吸收的差异（施罗德悖论）。解释的尝试很多，但仍然远远不够全面。然而，洞察吸附行为是至关重要的，因为它不仅控制膜的性能，但进一步影响准确的传质模型的发展，特别是当应用程序，如膜渗透蒸发或固体聚合物电解质燃料电池的关注，其中选择性膜同时暴露于气相和液相。使用Nafion®离聚物膜作为施罗德悖论的最突出的例子，本研究的目的是分别与气体和液体溶剂平衡的样品的吸水性的比较检查，涵盖了广泛的溶剂活动。对于液相吸附等温线的测定，开发了一种通用的方法，采用适当的预处理的聚合物消溶胀剂，这是禁止渗透到样品网络。两种平衡模式获得的吸附数据表明，严格相同的实验条件下提供，施罗德悖论解决。
Solvent sorption into polymeric membranes may be analysed by equilibrating the polymer sample either with the liquid or with the gaseous solvent. For a number of polymer/solvent systems, however, measurements at the point of saturation have revealed differences in solvent uptake from the liquid versus the corresponding vapour phase (Schroeder's paradox). Attempts at explanation are numerous, but still far from comprehensive. Yet, insight into the sorption behaviour is of crucial importance as it not only controls membrane performance, but further affects the development of accurate mass transfer models, especially when applications such as membrane pervaporation or solid polymer electrolyte fuel cells are concerned where a selective membrane is simultaneously exposed to a gaseous and a liquid phase. Using Nafion®ionomer membranes as the most prominent example of Schroeder's paradox, the present study aims at the comparative examination of water sorption for samples equilibrated with the gaseous and the liquid solvent respectively, covering a wide range of solvent activities. For the determination of liquid-phase sorption isotherms, a versatile method was developed, employing a suitably pretreated polymeric deswelling agent which is barred from penetration into the sample network. Sorption data obtained for both equilibration modes suggests that, strictly identical experimental conditions provided, Schroeder's paradox is resolved.