Matsumoto Hidetoshi, Yamamoto Ryotaro, Tanioka Akihiko
Department of Organic and Polymeric Materials and International Research Center of Macromolecular Science, Tokyo Institute of Technology, Mail Box S8-27, 2-12-1 Ookayama, Tokyo 152-8552, Japan.
J Phys Chem B. 2005 Jul 28;109(29):14130-6. doi: 10.1021/jp051585s.
In the present paper, we systematically examined the ion-pairing effect in low-water-content charged membranes. Cation- and anion-exchange membranes with various water contents and homogeneous fixed-charge distribution were prepared by radical copolymerization and then characterized by membrane potential measurements. The experimental results were analyzed by our recently developed theoretical model (Yamamoto, R.; Matsumoto, H.; Tanioka, A. J. Phys. Chem. B 2003, 107, 10615), which is based on the Donnan equilibrium, the Nernst-Planck equation for ion flux, and the Fuoss formalism for ion-pair formation between the fixed-charge group and the counterion in the membrane. The theoretical predictions agreed well with the experimental results for both cation- and anion-exchange membranes. This supported the belief that the ion-pairing effect was substantial in a low-water-content membrane system. Our theoretical analysis also showed the following results: (i) the dielectric constant in the membrane, epsilon(r), was smaller than the value in bulk water, (ii) the center-to-center distance of the ion pair, a, was independent of the water content of the membranes, and (iii) the charge effectiveness of all membranes, Q, was small (<0.35).
在本文中，我们系统地研究了低含水量带电膜中的离子配对效应。通过自由基共聚制备了具有不同含水量和均匀固定电荷分布的阳离子交换膜和阴离子交换膜，然后通过膜电位测量对其进行表征。实验结果采用我们最近开发的理论模型（山本，R.；松本，H.；谷冈，A.《物理化学杂志B》2003年，107卷，10615页）进行分析，该模型基于唐南平衡、离子通量的能斯特 - 普朗克方程以及膜中固定电荷基团与抗衡离子之间离子对形成的福斯形式。理论预测与阳离子交换膜和阴离子交换膜的实验结果都非常吻合。这支持了在低含水量膜系统中离子配对效应显著的观点。我们的理论分析还表明了以下结果：（i）膜中的介电常数ε(r)小于本体水中的值；（ii）离子对的中心到中心距离a与膜的含水量无关；（iii）所有膜的电荷效率Q都很小（<0.35）。
