Structural Tailoring of Polyaniline Synthesized by Acid-Assisted Polymerization at Room Temperature: Insights Into Polaron Dynamics

Abstract

This work presents a detailed study of the synthesis and characterization of polyaniline (PANI) using a novel acid-assisted polymerization method with varying ammonium persulfate concentrations. Two distinct PANI samples were synthesized at room temperature, resulting in different morphologies. Scanning electron microscopy revealed a porous nanofibrillar morphology for PANI1, while PANI2 exhibited a densely packed morphology. Raman spectroscopy confirmed the presence of semiquinoid units, with characteristic bands at similar to 1602 and similar to 1500 cm(-1) in both PANIs. UV-Vis spectroscopy revealed characteristic absorption bands at 259 and 428 nm, attributed to pi-pi* transitions and localized polarons transitions, respectively. Photoluminescence measurements identified emission bands at 2.26 and 2.18 eV, further supporting the presence of pi-pi* transitions. The observed energies suggest a mechanism involving the electron transfer coupled with reorganization energy, contributing to the observed spectral features. Fourier transform infrared spectroscopy confirmed the presence of key functional groups, including C-H bending vibrations at similar to 1140 cm(-1). Given that PANI is a p-type semiconductor with holes as the majority charge carriers, this work provides valuable insights into the structure-property relations of PANI synthesized via this novel synthesis method. These findings seem promising for the integration of PANI with carbon-based materials, forming a composite system (electrode) for advanced energy storage applications.