Electrochromic properties of polythiophene polyrotaxane film.
Electrochromic properties of polythiophene polyrotaxane film.
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DOI：
10.1021/la1043816
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发表时间：
2011-02
期刊：
影响因子：
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通讯作者：
Taichi Ikeda;M. Higuchi
中科院分区：
文献类型：
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作者：
Taichi Ikeda;M. Higuchi
研究了以聚噻吩为骨架，环二（对亚苯基百草枯）为四阳离子环芳的聚噻吩聚轮烷薄膜的电致变色性能。裸参比聚噻吩膜，即，不含四阳离子环蕃的聚噻吩也进行了表征。用原子力显微镜观察了薄膜的表面形貌和厚度。裸参比聚噻吩膜的表面具有微米级聚噻吩聚集体，这导致膜的颜色较暗，并且在电致变色过程中颜色对比度较小。聚噻吩聚轮烷由于四阳离子环芳烷抑制了聚噻吩链之间的分子相互作用而得到更均匀和更明亮的着色膜。电位阶跃计时电流法测量提供了可氧化位点的面积密度（Γ）和膜中电荷传输的表观扩散系数。根据L和Γ之间的线性关系，计算出聚噻吩聚轮烷和裸参考聚噻吩膜中的可氧化位点的浓度分别为1.3和2.4 mmol cm（-3）。有趣的是，聚噻吩聚轮烷膜提供了比裸参比聚噻吩膜显著更大的表观扩散系数。这一结果表明，电荷传输的速率决定步骤不是聚噻吩链之间的电子跳跃，但电荷补偿抗衡离子从溶剂到聚噻吩的传输。我们认为，四阳离子环蕃的抗衡阴离子提供了一个途径，允许电荷补偿抗衡阴离子从溶剂迁移到聚噻吩。在电致变色反应中，聚噻吩聚轮烷膜显示出比裸参比聚噻吩膜更快的颜色变化。这些结果表明，我们的聚噻吩聚轮烷是比裸参考聚噻吩更好的电致变色材料。
The electrochromic properties of a polythiophene polyrotaxane film consisting of a polythiophene backbone wrapped by the tetra-cationic cyclophane, cyclobis(paraquat-p-phenylene), were characterized. A naked reference polythiophene film, i.e., polythiophene without tetra-cationic cyclophane, was also characterized. The surface morphology and thickness of the film (L) were observed by atomic force microscopy. The surface of the naked reference polythiophene film has micrometer-scale polythiophene aggregates, which causes the darker color of the film and smaller color contrast in the electrochromic process. The polythiophene polyrotaxane gives a more homogeneous and brighter colored film owing to the suppression of molecular interactions between the polythiophene chains by the tetra-cationic cyclophanes. Potential-step chronoamperometric measurement provided the area density of the oxidizable sites (Γ) and the apparent diffusion coefficient of the charge transport in the film. From linear relationship between L and Γ, the concentrations of the oxidizable sites in the polythiophene polyrotaxane and naked reference polythiophene films were calculated to be 1.3 and 2.4 mmol cm(-3), respectively. Interestingly, the polythiophene polyrotaxane film afforded a significantly larger apparent diffusion coefficient than the naked reference polythiophene film. This result suggests that the rate-determining step of the charge transport is not the electron hopping between the polythiophene chains but the transport of charge-compensating counterions from the solvent into the polythiophene. We believe that the counteranions of the tetra-cationic cyclophane provide a pathway allowing the charge-compensating counteranions to migrate from the solvent to polythiophene. The polythiophene polyrotaxane film showed faster color change than the naked reference polythiophene film in the electrochromic reaction. These results indicate that our polythiophene polyrotaxane is a better electrochromic material than the naked reference polythiophene.