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

Evolution and Interdependence of Structure and Properties of Nanocomposites of Multiwall Carbon Nanotubes with Polyaniline

Structure–property relationships of nanocomposites of multiwall carbon nanotubes (MWCNTs) and polyaniline (PANI) doped with dodecylbenzenesulfonic acid (DBSA) are studied and discussed in terms of contribution of the PANI phase properties. Two phases of PANI-DBSA with different properties, such as a shell-wrapping carbon nanotube and separate neat PANI-DBSA domains, are revealed for the first time in the nanocomposites with a high or medium PANI-DBSA content. In the nanocomposites with lower PANI-DBSA contents (<40 wt %), only a core–shell morphology with ∼3 nm or lower thickness PANI shell on the nanotubes is observed. Under this condition, the degree of crystallinity of the PANI-DBSA shell increases almost 2-fold, and thermal stability of the nanocomposite grows sharply. As compared with the neat PANI-DBSA, this special PANI shell phase has more perfect molecular structure and is characterized by a reduced amount of DBSA. It is found that the latter is caused by a competition between the processes of doping of the formed PANI in the shell by the protonic acid and p-doping caused by the MWCNT surface. The nanocomposites demonstrate ppm/ppb range sensitivity to ammonia/methylamine gases with response times, which inversely depend on the PANI-DBSA contents and thickness of the shell