Analytical Basis of ion separation by use of growth of conducting zones associated with electrochemical switching of conducting polymers

通过改变掺杂溶液中的电极电位，电极上的芳香族导电聚合物薄膜的电导率可以发生显著改变，因为掺杂和解掺杂过程的行为类似于电极反应。当正向电势作用于薄膜时，导电区生长并从电极向溶液扩散，直到薄膜达到完全导电状态。相边界的出现归因于氧化物质的电子传导，氧化物质作为金属状电极与还原（绝缘）物质进行电化学反应。这种性质可能对离子种类敏感，因为离子对传导状态敏感。本工作致力于将这一性质应用于离子分离。首先，在准静态条件下确定了对开关行为具有重要意义的渗透阈值电位。这有助于估计导电带出现的势域。其次，利用光谱学研究了逆过程，发现其中包含慢弛豫。第三，发现并发展了一种利用磁感应电流评价电导率的有趣技术。这是事先没有预测到的，是本项目支持的新信息。第四，对开关的pH依赖性的研究正在进行中，这可能导致离子分离的分析。

The electric conductivity of an aromatic conducting polymer film on an electrode can be altered drastically by varying the electrode potential in a dopant solution, because the doping and the undoping processes behave like an electrode reaction. When positive potential is applied to the film, the conducting zone grows and propagates from the electrode toward the solution until the film becomes the fully conducting state. The appearance of the phase boundary is ascribed to the electronic conduction of the oxidized species which works as a metal-like electrode for the electrochemical reaction with the reduced (insulating) species. This property may be sensitive to ionic species because ions are sensitive to the conduction state. This work has been devoted to application of this property to separation on ions. At first, the percolation threshold potential, which is significant for the switching behavior, was determined under quasistatic conditions. The was helpful for estimating potential domains of appearance of the conducting zone. Secondly, the inverse process was investigated with a help of spectroscopy, and was found to include slow relaxation. Thirdly, an interesting technique of evaluating electric conductivity by use of mgnetically induced current was found and developed. This was not predicted in advance, and is new information supported by this project. Forthly, study of the pH dependenae of the switching is going on now, which may lead to analysis of ion separation..