【作者】 李慧；

【导师】 郝晓刚；

【作者基本信息】 太原理工大学 ， 高分子化学与物理， 2009， 硕士

【摘要】 电活性材料是电子-离子的混合导体。通过外加电路或添加化学试剂可以使其可逆的进行充电和放电。为了维持物相本身的电中性,在此过程中被转移的电荷会通过离子的置入或置出来补偿。具有不同化学性质的多种物系都具有这一特征,包括氧化还原或电子导电聚合物、含有混合价态的过渡金属无机络合物等。目前这类物质在电催化、传感器、水处理等方面得到了很大的应用。聚苯胺和聚吡咯等一系列导电聚合物具有较高的电导率,且易于制备、化学性质稳定,而成为了导电聚合物领域中的研究热点。这些聚合物在氧化还原过程中伴随着离子的交换具有离子交换性能,且这一性能得到了广泛的研究,有很好的应用前景。导电聚合物的制备方法有化学合成法,也有电化学聚合法。目前对于聚吡咯和聚苯胺薄膜电化学聚合及氧化还原过程的EQCM研究较少,而对此两个过程的研究直接关系到对薄膜离子交换性能的认识与运用。本文通过电沉积方法在镀铂石英晶片上制备出导电聚苯胺薄膜,并采用电化学石英晶体微天平(EQCM)技术对薄膜的聚合及苯酚溶液中的氧化还原过程进行了较详细的研究。在0.5mol/L的硫酸溶液中采用循环伏安法结合EQCM来考察聚苯胺薄膜在完全还原态(leucoemeraldine,LEB)—半氧化态(emeraldine,EB)之间以及完全还原态—完全氧化态(pemigraniline,PNB)之间电活性及相应的稳定性;在纯苯酚和不同浓度的硫酸+苯酚的混合溶液中采用恒电压阶跃法通过控制电位使薄膜处于半氧化态或完全还原态来考察薄膜电控分离苯酚的性能,并经傅立叶红外光谱做进一步分析。实验结果表明:聚苯胺薄膜在完全还原态—半氧化态之间循环扫描具有较好的电活性和稳定性。薄膜处于半氧化态时溶液中的苯酚置入膜中,薄膜处于完全还原态时膜中的苯酚又释放到溶液中。通过控制薄膜的电位可以方便地控制苯酚的置入与释放,从而达到分离溶液中苯酚的目的。通过电沉积方法在铂基体上制备出十二烷基磺酸根掺杂聚吡咯(PPy/DS-)薄膜,并采用EQCM技术对薄膜的聚合过程进行了较详细的研究。在碱金属和碱土金属溶液中比较考察了薄膜电极的电控离子交换性能。在0.1mol/L的NaNO3、KNO3和CsNO3以及0.1mol/L的Ca(NO3)2和Mg(NO3)2溶液中通过循环伏安法,并结合电化学石英晶体微天平(EQCM)技术和XPS能谱考察了PPy/DS-薄膜在不同溶液中的电活性、电化学行为和离子的置入置出机制;在0.1mol/L的KNO3、CsNO3以及Mg(NO3)2溶液中通过考察薄膜离子交换容量随循环次数的衰减情况来分析循环寿命。实验结果表明:聚吡咯薄膜具有良好的电活性;膜电极在进行氧化还原扫描的同时既伴随着阳离子的交换又伴随着阴离子的交换,可根据需要通过控制扫描电位来单独交换阳离子或阴离子;在CsNO3溶液中薄膜在-1.05V—0.14V范围内循环扫描过程中只伴随着Cs+的交换;在碱金属的硝酸盐中薄膜的稳定性较碱土金属的硝酸盐中高,尤其在CsNO3溶液中更高。更多还原

【Abstract】 Electroactive materials compasses mixed (electron-ion) conducting materials whose bulk phases can be charged/discharged electronically from an external electric circuit or by electrochemical agents. To remain the electroneutrality of the phase the transferred electronic charge must be compensated by the incorporation/expulsion of ionic species. Such a phenomenon is characteristic of numerous systems with very diverse chemical natures, including redox or electronically conducting polymers, inorganic solids with mixed-valence transition metals. At present, these materials have been applied in electrocatalysis, sensors, water treatment and so on.A series of electroactive polymers such as polyaniline (PAn) and polypyrrole (PPy) are the most investigated polymers because they have higher conductivity, a good stability in the air and can be prepared easily. The redox processes of these polymers are accompanied by ion exchange, i.e. they have ion exchange property. The property has been investigated comprehensively. Conductive polymers can be prepared by chemical method or electropolymerization. In recent years, few EQCM investigations of electropolymerization and redox process for PAn and PPy have been reported, but the investigations relate to our comprehension and application for ion exchange properties directly.Electroactive PAn thin films were synthesized on platinum substrates by electrodeposition, electrochemical quartz crystal microbalance (EQCM) was adopted to investigate the preparation process. In 0.5mol/L H2SO4 solution, Cyclic voltammetry (CV) and EQCM were used to investigate electroactivity and stability when thin film was controlled between (leucoemeraldine) LEB and (emeraldine) EB or between (leucoemeraldine) LEB and (pemigraniline) PNB. In pure phenol or mix solutions of phenol and H2SO4, chronocoulometry and FTIR were used to investigate the electrochemically controlled phenol separation property of thin film by controlling potential to adjust LEB and EB of film. Experimental results show that PAn prepared by electrodeposition has good electroactivity and stability when film is controlled between LEB and EB during cycling process. If film lies in EB, phenol in electrolyte will enter into the film; If film lies in LEB, phenol entered into the film will release into electrolyte again. We can make phenol enter into film or release from film to electrolyte freely by controlling potential, then the phenol in solution can be separated.PPy doped with dodecylsulfate (PPy/DS-) thin films were synthesized on platinum substrates by electrodeposition, EQCM was adopted to investigate the preparation process. Film-electrode systems were investigated as electrochemically switched ion exchange materials in electrolytes of alkali-metals and alkaline-earth metals. In 0.1mol/L NaNO3, KNO3, CsNO3 and 0.1mol/L Ca(NO3)2, Mg(NO3)2 solutions, Cyclic voltammetry (CV), Electrochemical quartz crystal microbalance (EQCM) and X ray photoelectron (XPS) were used to investigated electroactivity, electrochemical behavior and loading mechanism of PPy/DS- film electrodes. In 0.1mol/L KNO3, CsNO3 and 0.1mol/L Mg(NO3)2 solutions, ion exchange capacity decreasing with cycle number was investigated to analyze cycle life of thin film. Experimental results show that PPy/DS- thin film has good electroactivity; the oxidation and reduction processes of PPy/DS- thin film were accompanied by cation exchange and anion exchange simultaneously, cation or anion can be exchanged singly according to demand by controlling scan potential; in CsNO3 solution, only Cs+ is exchanged when thin film is scanned between -1.05V and 0.14V; The cycle life is better in alkali-metals nitrates than in alkaline-earth metals nitrates, especially much better in CsNO3 solution.更多还原