Comparative study of polyaniline cast films prepared from enzymatically and chemically synthesized polyaniline

Enzymatically and chemically synthesized polyaniline (Pani) were used to prepare free standing cast films from N-methyl-2-pyrrolidinone solutions. The films were redoped by immersion in hydrochloric or p-toluensulfonic acid solutions. Physical and chemical properties were investigated using UV–visible, Fourier transform Infrared and X-ray photoelectron (XPS) spectroscopic techniques. Analysis by XPS revealed changes in the –N/NH– ratio that indicate cross-linking in the surface of both types of films, whereas FT-IR indicates cross-linking in the core of films prepared with enzymatically synthesized Pani. Such changes can be attributed to the catalyzing effect of sulfonic residues and chain defects of the polymer. Consequently, the degree of doping of the films prepared with enzymatically synthesized Pani was lower compared to films prepared with chemically synthesized Pani.