Spectroscopic investigation of water-soluble polyaniline copolymers

The chemical copolymers of m-aminobenzene sulfonic acid with O-anisidine (POABSA) and O-toluidine (POTBSA) have been synthesized. Polymers are water soluble and self-doped. The peak in IR spectra at 1100–1160 cm−1 shows the presence of SO3 group in the polymer backbone. Self-doped copolymers exhibit a strong and wide range of polaron absorption at 772–943 nm in m-cresol, due to the conformational changes induced by polymer solvent interaction. Copolymers also display a strong polaron transition in m-cresol with LiCl. Salt acts as a pseudo-doping agent and extends ‘coil-like’ conformations. The highest thermal activation is monitored at 70 °C, above that temperature (<100 °C) overcompensation of thermal activation effect is observed. The electrical conductivity of copolymers is low (10−4 to 10−5 S cm−1), caused by strong steric effect between SO3 and OMe/Me groups.