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.