Local Structure and Dynamics of Imidazole Molecules in Proton-Conducting Poly(vinylphosphonic acid)-Imidazole Composite Material
Local Structure and Dynamics of Imidazole Molecules in Proton-Conducting Poly(vinylphosphonic acid)-Imidazole Composite Material
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DOI：
10.1021/ma5013418
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发表时间：
2014-11-11
期刊：
影响因子：
5.5
通讯作者：
Ida, Tomonori
中科院分区：
文献类型：
--
作者：
Mizuno, Motohiro;Iwasaki, Ayano;Ida, Tomonori
许多质子导电聚合物，包括咪唑及其衍生物，已被开发用于固体电解质燃料电池。据认为，质子传导是由与咪唑分子在这些材料中的再取向运动相关的Grotthuss机制引起的。然而，在对咪唑分子运动进行详细研究之后，对咪唑分子的重取向运动与质子传导之间关系的分析仍然很少。采用固体核磁共振技术研究了聚乙烯基膦酸（PVPA）咪唑（Im）复合材料（PVPA/xIm，其中x为Im与聚合物重复单元的摩尔比）的分子运动及其对质子导电性的影响。在20 ~ 50 ℃范围内，Im分子发生赝各向同性转动，各向异性较小，占90%以上，PVPA/2 Im分子发生转动振动的比例小于10%。紧段，其中Im分子进行旋转振动，防止长距离质子传导。在60 ℃以上，在PVPA/2 Im中证实了伴随Im分子的伪各向同性旋转的有效质子传导。
Many proton-conducting polymers, including imidazole and its derivatives, have been developed for their applications in solid electrolyte fuel cells. It is thought that proton conduction is caused by the Grotthuss mechanism associated with the reorientational motion of imidazole molecules in these materials. However, there are still very few analyses of the relation between proton conduction and the reorientational motion of imidazole molecules following the detailed investigation of the molecular motion of imidazole. In the present work, molecular motions and their influence on proton conductivity were investigated for poly(vinylphosphonic acid) (PVPA)imidazole (Im) composite material (PVPA/xIm, where x is the molar ratio of Im to polymer repeat unit) by solid-state NMR. Between 20 and 50 degrees C, the Im molecule undergoing pseudoisotropic rotation with small anisotropy accounted for more than 90% and that undergoing rotational vibration for less than 10% for PVPA/2Im. The tight segment, where Im molecules undergo rotational vibration, prevents long-range proton conduction. Above 60 degrees C, efficient proton conduction accompanied by pseudoisotropic rotation of the Im molecules was confirmed in PVPA/2Im.