Polyaniline precipitation in aqueous medium: from bulk aggregates to nanoparticles

The effect of inorganic salt on the morphology and nucleation of polyaniline nanofibers synthesized via self-assembly

Polyaniline (PANI), due to the various and controllable shapes, the environmental stability, the excellent physical and chemical property, has gained significant attention. PANI with abundant morphologies were successfully prepared through adjusting and controlling the state of the initial micelle-like in the micelle-like system composed by aniline and organic acids with relatively weak intermolecular interaction. Although the influence of the inorganic salts on their morphology, including the surface and the diameter, was investigated, the influence of salt on the nucleation of PANI was still unclear. Therefore, PANI nanofibers were fabricated through the addition of inorganic salt such as NaCl, MgSO₄ and AlCl₃ into the micelle-like composed of aniline and D-camphor-10-sulfonic acid. The influence of types and concentration of inorganic salts, doped acids and temperature on PANI was studied by Transmission Electron Microscope (TEM), UV-vis and Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy. In addition, in situ UV-vis and ¹H Nuclear Magnetic Resonance technology (NMR) were applied to observe the process of aniline polymerization, and it was indicated the polymerization rate of aniline changed after the addition of inorganic salt NaCl into the initial solution.