Surface, Solvent, and Anion Effects on Polaronic Transitions in New Polyaniline Composites and Nanocomposites

Abstract

In this research, the synthesis of novel conductive composites and nanocomposites of the polyaniline (PANI) is reported by the chemical and oxidative insitu polymerization of aniline in the presence of silica- and nanosilica-supported perchloric acid as well as ammonium peroxy disulfate without using a solvent (solid-state condition) at room temperature and Also, changes in polaron mutations under changing conditions are analyzed. The structure, size, and morphology of all samples were identified using FT-IR, UV-Vis, SEM, AFM, and XRD, spectroscopy methods. The conductivity of the samples was determined by using the four-probe technique, Cyclic Voltammetry, and their values were in the range of conductive polymers. According to AFM and SEM images, silica particles have been thoroughly coated by PANI, and the particle sizes of composite and nanocomposite were in the range of 0.5-4μm and 60-90nm, respectively. Also, the X-ray diffraction (XRD) shows that the nanosilica-supported perchloric acid was crystalline whereas the synthesized nanocomposite was semi-crystalline. Furthermore, the SEM, AFM, and XRD results confirm strong core-shell morphology in obtained nanocomposites. The size of the polymer particles is directly related to the conductivity of the polymer. The UV Visible study showed that the effect of polar solvents with high dielectric constant such as DMF and MeOH is more for smaller particles such as nanocomposite. Due to more interaction of solvent with polymer chromophores groups, their effect is stronger. They reduce energy levels and increase energy gap transfer. They increase the number of polaronic transitions. Chloride anion, compared to perchlorate anion (multi-atomic), due to more connection centers and a specific type of connection, remains in the salt polymer structure after work-up with H2O and causes the formation of a two-layer coating and an increase in the coating surface. This issue in XRD causes the broadening of the peak and the amorphous appearance compared to the NSSPA spectrum and prevents the emergence of separate and sharp peaks. Due to the increase in the surface and size of polymer particles in the structure of the composite, the conductivity is slightly higher than that of the nanocomposite. Due to the increase in the surface and size of polymer particles in the structure of the composite, the conductivity is slightly higher than that of the nanocomposite. Therefore, it can be concluded that in resistors that are used to limit a certain amount of electric current, the nanocomposite structure is preferable to the composite structure.