苯胺在十二烷基苯磺酸/水体系中的乳液聚合过程研究

利用光学显微镜和扫描电镜,对以水为介质、十二烷基苯磺酸(DBSA)为乳化剂的苯胺乳液聚合过程进行监测,发现苯胺在水体系中与DBSA反应形成DBSA-苯胺盐的棒状聚集结构,讨论了DBSA、苯胺、氧化剂的配比及浓度对聚合过程中棒状聚集结构的长度和数量及生成聚苯胺的电导率的影响,提出苯胺在DBSA/水体系中的乳液聚合反应是在胶束表面进行的,而棒状聚集结构中的DBSA-苯胺盐单体经水相扩散到乳胶粒子中,形成颗粒状的聚苯胺.

Emulsion Polymerization of Aniline in Dodecylbenzenesulphonic Acid/Water System

Polyaniline(PANI) is one of the most promising conducting polymers for its high environmental stability,tunable electrical properties and relatively low cost.Anyway,one of the problems associated with its successful application in many areas,such as organic conductors,actuators,electromagnetic shielding,light-emitting diodes and gas-separation membranes,is the difficulty in processing of this material due to its very low solubility in different organic solvents.One of the approaches to improve the processability of polyanilines in solvents is to prepare them by chemical emulsion polymerization of aniline in the presence of various surfactants such as camphorsulphnic acid(CSA),dinonylnaphthalenesulphnic acid(DNNSA) and dodecylbenzenesulphnic acid(DBSA),which was used as emulsifier and dopant,simultaneously.However,many researches have focused on the influences of the aniline and/or surfactant concentration,time and temperature etc on the conductivity and solubility of the resulting polyanilines,there are no detailed reports on the monitoring of the emulsion polymerization process and the emulsion polymerization mechanism of aniline in the presence of surfactant,that is DBSA.And the location and morphology of aniline or its anion in the reaction medium are important that they can give the useful information of reaction mechanism and properties of the final product.In this report,the emulsion polymerization of aniline(Ani) in a system consisted of dodecylbenzenesulphonic acid(DBSA)-water-aniline was carried out using ammonium peroxydisulfate(APS)as oxidant.The microscope and SEM was used to monitor the polymerization process.The effects of the molar ratio of DBSA/Ani/APS and the concentration of DBSA and Ani on the morphologies of polymerization systems and the conductivity of the resulting polyanilines were investigated.It shows that in all cases Ani and DBSA combined and formed micro-rods before the polymerization,which became shorter and fewer during the polymerization process,meanwhile the resulting polyanilines possessed granular particle morphology.Therefore we proposed that the polymerization mechanism of aniline in the DBSA-water-aniline system was as follows:DBSA first reacted with aniline to give DBSA-aniline salts,which were insoluble in water and self-assembled into micro-rod aggregates before the emulsion polymerization occurred.Any way the emulsion polymerization of aniline in DBSA/water system was just took place in the micelles as the excess DBSA in the reaction system could form micelles solubilized aniline.With proceeding polymerization reaction,DBSA-aniline salts in the micro-rods were dissolved and diffused into the latexes to give resulting polyaniline doped by DBSA in granular particle morphology.