Synthesis and characterization of 2-methylimidazole end capped Zwitter ion functionalized Polyaniline

Due to the lack of functional groups, the processability of polyanilines (PANIs) are limited. Poor solubility in common solvents, high rigidity and hydrophobicity are the important problems associated with PANI. To enhance its processability, acid and amine groups were grafted onto the PANI backbone via a Friedel-Crafts (FC) alkylation reaction, carried out at 85°C for 6 hours under a nitrogen atmosphere with vigorous stirring. Prior to this, the PANI backbone was synthesized through free radical (FR) solution polymerization, initiated by peroxy disulphate (PDS), using aniline monomer at 0–5°C under nitrogen purging. A key modification during synthesis was the inclusion of 2 -methylimidazole ( 2 MI), which imparted hydrophilicity and facilitated end-capping of the polymer chains. The functionalized PANIs were thoroughly characterized by various analytical tools, antimicrobial properties and thermal properties. Following acid functionalization, the water contact angle (WCA) increased to 61.4°, attributed to the formation of Zwitter ionic structures, as evidenced by an FTIR peak at 1640 cm⁻¹. This modification also significantly improved the water solubility of PANI. The % yield of A3 sample was found to be low due to the availability of few reaction cite on the aromatic ring of PANI for second grafting reaction. A plausible reaction mechanism was proposed based on the experimental findings, which were carefully analyzed and compared with values reported in the literature.