在线紫外-可见光谱研究ITO导电玻璃电极上苯胺与对苯二胺的电化学共聚及其产物的表征

Study on Electrochemical Copolymerization of Aniline with p-Phenylenediamine on ITO Electrode by in situ UV-Vis Spectroscopy and Characterization of the Copolymer

苯胺与对苯二胺在ITO导电玻璃上发生了电化学共聚合,在0.5mol/LH2SO4水溶液的纯苯胺和苯胺与对苯二胺共聚时的循环伏安曲线以及其对应的在线紫外-可见光谱表明对苯二胺的加入除了发生共聚外,也使聚合的速率明显加快;而且纯苯胺在循环伏安电化学聚合时在430nm处出现的吸收带因对苯二胺的加入而消失,说明对苯二胺的加入使聚合的机理与纯苯胺的聚合机理有明显不同,主要原因是苯胺产生的反应中间体可能很快与对苯二胺的阳离子自由基反应聚合.在导电玻璃ITO上的聚合物膜的反射傅立叶红外光谱表明,对苯二胺的加入可能产生了具有1,2取代模式结构,这说明了对苯二胺结合进入到聚合物中.这种共聚使得产物的表面形貌也发生了变化,聚合物扫描电镜图表明对苯二胺的加入有利于纤维状的表面形貌产生,纤维的直径可达到50nm粗细;同时用在线紫外-可见光谱研究了纯聚苯胺和共聚物随电位变化的电变色性质,结果表明在0～0.6V之间共聚物与纯聚苯胺的在线紫外-可见光谱有明显的不同,且共聚物的电变色可逆性比纯聚苯胺好;同时SEM图也表明在0.8V电位下聚苯胺和共聚物表面形貌发生了团聚.

It was observed by in situ UV-Vis spectrometry that the polymerization of p-phenylenediamine and the electrocopolymerization between aniline and p-phenylenediarnine happened by cyclic voltammetry in a 0.5 mol/L sulfuric acid media, and that the polymerization reactions became faster due to the addition of p-phenylenediamine. Experimental results showed that the absorbance band at 430 nm in in situ UV-Vis spectra disappeared because of the presence of p-phenylenediamine. The reason leading to these results might be that the cation radical intermediate produced from aniline reacted with the p-phenylenediamine cation radical during polymerization. It was a direct evidence which indicated that the addition of p-phenylenediamine changed the mechanism of the electro-polymerization of aniline on an ITO electrode in a 0.5 mol/L sulfuric acid solution. The reflectance FTIR spectra of films deposited on the ITO electrode was obtained, which showed that p-phenylenediamine could be incorporated into the copolymer films by 1,2- or 1,2,3-substituted modes. The SEM images of the films showed that the additional p-phenylenediamine could change markedly morphology of the films and promoted the growth of fibrous morphology with a large area.The diameter of the fiber in the film grown on the ITO electrode might reach 50 nm. The electrochromic behavior of the polymer films was studied in detail. At the potential ranged from 0.0 to 0.6 V, the in situ UV-Vis spectra of the copolymer film deposited on the ITO electrode was obviously different from that of polyaniline film on the ITO electrode. The electrochromic reversibility of the copolymer was better than that of polyaniline. Furthermore, SEM morphology images indicated that electrolyzing polyaniline and copolymet on the ITO electrode at 0.8 V in the 0.5 mol/L H2SO4 made them aggregate.