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The transformation and degradation of Nafion® solutions under ultrasonic treatment. The effect on transport and mechanical properties of the resultant membranes
Polymer Degradation and Stability ( IF 6.3 ) Pub Date : 2020-05-18 , DOI: 10.1016/j.polymdegradstab.2020.109229
Ekaterina Yu Safronova , Gerald Pourcelly , Andrey B. Yaroslavtsev

This work addresses the study of the effect of ultrasonic (US) treatment on the properties of alcohol solutions of perfluorinated sulfonic acid polymer Nafion® and cast membranes. The effect of the duration of US treatment on the physico-chemical properties (water uptake, transport and mechanical properties) of the resulted membranes is described for the first time. Upon the US treatment, viscosity of the polymer solutions irreversibly decreases due to deagglomeration and rupture of macromolecular chains. As a result of the US treatment, mechanical properties of the Nafion® membranes are deteriorated. The dependences of water uptake and conductivity of the Nafion® membranes in the proton form on sonication time pass the maximum (at 30–45 min). Due to the sonication of polymer solutions, proton conductivity of the membranes increases by 40–45%. Upon extended sonication, the content of sulfonic acid groups decreases, and carboxyl groups are formed at the ends of macromolecules. Thus, water uptake of the membranes prepared from the polymer solutions after the US treatment for 60 min decreases, and conductivity of the obtained membranes in the H+-form is reduced. However, for the Nafion® membranes in the Na+-form, as the duration of the US treatment is extended, their conductivity and diffusion permeability tend to increase due to the enhanced connectivity of pores and channels as well as due to the participation of carboxyl groups in the ionic transport. Upon extended sonication, selectivity of the cation transfer through the membranes is reduced. The results of this work highlight the importance of the proper selection of favorable conditions of the US treatment of the solutions of perfluorinated sulfonic acid polymers for the preparation of hybrid membranes and for the development of catalytic layers of membrane-electrode assemblies for fuel cells.



中文翻译:

Nafion®溶液在超声处理下的转化和降解。对所得膜的运输和机械性能的影响

这项工作致力于研究超声波(美国)对全氟磺酸聚合物Nafion®和流延膜的醇溶液性能的影响。首次描述了US处理持续时间对所得膜的理化性质(吸水率,传输率和机械性能)的影响。在US处理中,由于高分子链的解聚和断裂,聚合物溶液的粘度不可逆地降低。经过美国的处理,Nafion®膜的机械性能下降。质子形式的Nafion®膜的吸水率和电导率对超声处理时间的依赖性最大(在30-45分钟时)。由于聚合物溶液的超声处理,膜的质子传导率提高了40–45%。长时间超声处理后,磺酸基团的含量降低,并且在大分子的末端形成羧基。因此,在US处理60分钟后,由聚合物溶液制备的膜的吸水率降低,并且所得膜在H中的电导率降低。+-形式减少。但是,对于Na +形式的Nafion®膜,随着US处理时间的延长,由于孔和通道的连通性增强以及羧基的参与,其电导率和扩散渗透性趋于增加。离子传输中的基团。在延长的超声处理下,穿过膜的阳离子转移的选择性降低。这项工作的结果凸显了正确选择美国处理全氟化磺酸聚合物溶液的有利条件的重要性,以制备混合膜和开发燃料电池膜电极组件的催化层。

更新日期:2020-05-18
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