Influence of Dispersed Nanoparticles on the Kinetics of Formation and Molecular Mass of Polyaniline

Using a combination of the open circuit potential and pH profiles of aniline (An) polymerization and their mathematical treatment, we develop a new convenient semiquantitative approach to determine the influence of the dispersed nanoparticles (e.g., TiO2 nanoparticles) on the kinetic features of this process and molecular mass of the formed polyaniline (PANI). It is revealed that the reciprocal values of the polymerization stages, namely, the duration of the induction period, of homogeneous and heterogeneous pernigraniline (PN) accumulation, and of PN reduction with An, are linear functions of the weight fraction of the nanoparticles. We found that when nanoparticles are added the weight-averaged molecular weight of PANI initially increases from 56 000 to 79 000 and the polydispersity index drops from 3.9 to 1.7. However, at high TiO2 concentrations, the former dramatically decreases, whereas the latter increases. We use the relative proton concentration as a function of time and the different extents of acceleration of the consecutive stages of An polymerization to explain the changes in the molecular weight distribution of PANI with different contents of TiO2 nanoparticles in the polymerization medium.