Klein Robert J, Zhang Shihai, Dou Shichen, Jones Brad H, Colby Ralph H, Runt James
Department of Materials Science and Engineering and the Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Chem Phys. 2006 Apr 14;124(14):144903. doi: 10.1063/1.2186638.
A novel method is presented whereby the parameters quantifying the conductivity of an ionomer can be extracted from the phenomenon of electrode polarization in the dielectric loss and tan delta planes. Mobile ion concentrations and ion mobilities were determined for a poly(ethylene oxide)-based sulfonated ionomer with Li(+), Na(+), and Cs(+) cations. The validity of the model was confirmed by examining the effects of sample thickness and temperature. The Vogel-Fulcher-Tammann (VFT)-type temperature dependence of conductivity was found to arise from the Arrhenius dependence of ion concentration and VFT behavior of mobility. The ion concentration activation energy was found to be 25.2, 23.4, and 22.3+/-0.5 kJmol for ionomers containing Li(+), Na(+), and Cs(+), respectively. The theoretical binding energies were also calculated and found to be approximately 5 kJmol larger than the experimental activation energies, due to stabilization by coordination with polyethylene glycol segments. Surprisingly, the fraction of mobile ions was found to be very small, <0.004% of the cations in the Li(+) ionomer at 20 degrees C.
本文提出了一种新方法，通过该方法可以从介电损耗和损耗角正切平面中的电极极化现象中提取量化离聚物电导率的参数。测定了基于聚环氧乙烷的磺化离聚物与Li⁺、Na⁺和Cs⁺阳离子的移动离子浓度和离子迁移率。通过研究样品厚度和温度的影响，证实了该模型的有效性。发现电导率的Vogel-Fulcher-Tammann（VFT）型温度依赖性源于离子浓度的Arrhenius依赖性和迁移率的VFT行为。对于含Li⁺、Na⁺和Cs⁺的离聚物，离子浓度活化能分别为25.2、23.4和22.3±0.5 kJ/mol。还计算了理论结合能，发现由于与聚乙二醇链段配位而稳定，理论结合能比实验活化能大约5 kJ/mol。令人惊讶的是，发现移动离子的比例非常小，在20℃时Li⁺离聚物中阳离子的比例小于0.004%。
