Electrochromism of Conducting Polymer Polypyrrole Films and the Elucidation of its Deterioration Mechanism

聚吡咯等导电聚合物的电导率和光吸收发生变化，与离子的掺杂和解掺杂相对应，有望用作电致变色器件。然而，由于这些聚合物在机械上是硬而脆的，并且在重复使用时只有很短的循环寿命，因此很难将它们用于实际应用。为了克服这一困难，弄清导电聚合物电致变色的恶化机理是非常有效的。本研究采用CCD摄像机、密度梯度离心法和原子力显微镜（AFM）对聚吡咯（PPy）薄膜在电解质溶液中施加循环电压时特性的转变进行了微观观察。从本研究中我们得出如下结论。(1)电电解质离子循环掺杂/脱掺杂后，在PPy薄膜中发现了针孔。(2)随着施加电压的循环次数的增加，引脚孔的数目和总电压增加。(3)电电解质离子循环掺杂/脱掺杂后，PPy薄膜的密度增加。(4)原子力显微镜（AFM）表面形貌观察表明，电解液离子循环掺杂/脱掺杂后，PPy薄膜的晶粒尺寸缩小。(5)电沉积吡啶吡啶薄膜电致变色的恶化是由于吡啶吡啶薄膜在电电解质离子的循环掺杂和解掺杂过程中收缩所致。同时，为了克服这些缺陷，提高其实际性能，我们开发了一种新的导电方法，使聚合物薄膜具有良好的耐久性；聚吡咯（PPy）和聚乙烯醇（PVA）的复合薄膜。利用这种PPy/PVA复合材料，我们研制了一种固态电致变色显示器件。在(]SY.+-直流电压的反复交替作用下，器件的颜色变化（黑色和透明黄色）超过2X10<@D15@>D1次。(0.9)。少

Conducting polymers such as polypyrrole are expected to utilize as electrochromic devices, because they change in their electrical conductivity and absorption of light, corresponding to doping and undoping of ions. However, it has been difficult to fit them for practical use, because these polymers are mechanically hard and brittle and they have only a short cycle-life when used repeatedly. In order to overcome the difficulty, it is very effective to clarify the deterioration mechanism of electrochromism of conducting polymers. In this study, the transition of the characteristics of polypyrrole (PPy) films while applying cyclic voltage in electrolyte solution was studied by the microscopic observation with a CCD video camera, a density gradient centrifugation method, and atomic force microscopy (AFM).From this study we conclude as follows. (1) Pin holes were observed in the PPy film with cyclic doping/undoping of electrochrolyte ions. (2) The the number of the pin holes and the total a … More rea of the pin holes were increased as the increase of the cyclic number of the voltage application. (3) The density of PPy films were increased after cyclic doping/undoping of electrochrolyte ions. (4) The surface morphology observed by AFM shows that the grain size of PPy films shrunk after cyclic doping/undoping of electrochrolyte ions. (5) The deterioration of electrochromism appeared on the electrodeposited PPy films was caused by the shrinkage of PPy films during cyclic doping and undoping of electrochrolyte ions.And also, to overcome these defects and to improve their practical performance, we developed a new method of conducting polymer films of good durability ; composite films of Polypyrrolc (PPy) and the Poly vinyl-alcohol (PVA). By using this PPy/PVA composite, we developed a solid-state device of electrochromic display. The device showed color change (black & transparent yellow) more than 2X10<@D15@>D1 times under repeated and alternate application of DC voltages of (]SY.+-。[) 0.9. Less