Influence of the aniline concentration on the morphology and property of polyaniline nanotubes and their polymerization mechanism

Polyaniline is a kind of polymer material with excellent electrochemical performance, and it stands out among a number of conductive polymer materials owing to its low cost, easy availability of raw materials, and excellent physical and chemical properties. However, the poor processability of polyaniline impedes its broad application. Preparing nanosized structure and introducing big molecular organic acids as dopant are practical strategies to solve this problem. Here using ammonium persulfate as oxidant, sodium dodecyl sulfate as surfactant, and 3,5-dinitrobenzoic acid as doping acid, polyaniline nanotubes were successfully prepared via emulsion polymerization method and characterized by various measurements. The influence of aniline concentration on the morphology and property of the product was explored. The polymerization mechanism of polyaniline nanotubes was discussed in detail based on the analysis of the microscopic morphology. As the concentration of aniline monomer increases, the position of the characteristic absorption peak in the infrared spectrum of the polyaniline main chain remains almost unchanged, but the ratio of benzene to quinone gradually increases. Along with the increasing aniline concentration, the crystallinity of polyaniline gradually decreases from 56.21% to 40.37%. In addition, the optimal conductivity is 2.05x10-2 S/cm when the concentration of aniline monomer is 0.5 mol/L.