导电聚合物超薄膜的制备及性能表征

采用修饰LB膜法制备了导电聚合物聚-3,4-乙烯二氧噻吩/硬脂酸(PEDOT/SA)复合超薄膜. 将硬脂酸(SA)/FeCl3 LB膜暴露于EDOT单体气氛中, EDOT 单体在多层膜中聚合, 制备了PEDOT/SA多层复合LB膜. 紫外-可见光-近红外(UV-Vis-NIR)吸收光谱和X射线光电子能谱(XPS)分析表明EDOT单体在多层膜中发生聚合并生成PEDOT导电聚合物. 扫描电子显微镜(SEM)分析显示生成的PEDOT导电聚合物颗粒分散于硬脂酸LB膜中, 被LB 膜所包裹. 二次离子质谱(SIMS)及XPS分析还发现S元素含量随LB 膜的深度变化而变化, 表明PEDOT 较好地分散于多层膜中. 采用四探针电导率仪对复合多层膜的电导率进行了测试, 结果显示60 层复合LB 膜的电导率为2.6 S·cm-1, 比普通PEDOT薄膜的电导率高一个数量级, 且表现出较好的掺杂/脱掺杂能力. 研究还发现复合膜电导率与薄膜在EDOT 单体中处理时间有关, 处理时间至120 min 后电导率达到最大值并趋于稳定, 氧化剂浓度较低可能影响EDOT在LB膜中的聚合反应速率. 对复合LB 膜的气敏特性进行了分析, 发现在较低气体浓度范围(φ<30×10^-6), PEDOT 复合LB 膜有较快的反应速率, 气敏性与气体浓度呈非线性. 在较高浓度范围(φ=(30-120)×10^-6), 气敏性与浓度呈较好的线性关系. PEDOT复合LB膜对HCl气体表现出较好的响应恢复特性. 同时对PEDOT 复合膜相关的导电机理及气体敏感机理进行了分析.

Preparation and Properties of Conducting Polymeric Ultrathin Films

A multilayer ultrathin filmof poly(3,4-ethylene dioxythiophene) (PEDOT) was first prepared by a modified Langmuir-Blodgett (LB) technique. The polymerization of EDOT monomer occured in a multilayer as-prepared LB film by exposing the filmto EDOTvapor. The formation of PEDOTparticles in the LBfilmwas confirmed by UV-Vis-near IR (UV-Vis-NIR) absorption spectrumand X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) investigation of the filmsurface exhibited small PEDOTparticles distributed in stearic acid (SA) LBfilms. Secondary ion mass spectrometry (SIMS) was employed to analyze the location of PEDOT formed and the results showed that PEDOT was well confined in the multilayer structure. A 60-layer PEDOT LB film had higher conductivity (2.6 S·cm-1) than a conventional PEDOT film, and exhibited excellent doping/dedoping characteristics. An investigation of the relationship between film conductivity and exposure time on EDOT ambience revealed that the film obtained steady conductivity after 120 min and it was concluded that the lower oxidizer density in LB film might slow the polymerization speed of EDOT. In a study of sensitive characteristics, the PEDOT film showed faster and nonlinear responses to analyte gas in a lower concentration (φ<30×10^-6), and exhibited a linear response to analyte in a higher concentration (φ=(30-120)^10-6). The result of gas sensitivity also showed that the film had excellent reversible and reproducible response to HCl vapor. The mechanismof conductivity and gas sensitivity of composite LB films were also included.