Secondary doping phenomena of two conductive polyaniline composites

Effects of secondary doping of polyaniline (PAn) composites, prepared by in situ emulsion polymerization of aniline in the presence of chlorosulfonated polyethylene (CSPE) or styrene-butadiene-styrene triblock copolymer (SBS) and dodecylbenzenesulfonic acid (DBSA), on conductivity were studied. In situ observations of the secondary doping process using electronic spin resonance (ESR) and ultraviolet-visible-near infrared (LN-VIS-NIR) spectrophotometry were carried out. In situ observation of dedoping process of the two composites with or without previous secondary doping using UV-VIS spectrophotometry was also performed. The in situ observation of dedoping process with ammonia solution for both composites with or without previous secondary doping via UV-VIS spectrophotometry indicated that the secondary doping caused the absorption peak at 560 nm for benzoid-quinoid structure to shift to red and broaden to form a shoulder at 710 nm. This fact demonstrates that the pi -conjugation of the benzoid-quinoid structure of PAn chains increases due to the expanding of the coiled PAn chains induced by the secondary doping. It was also found that the increase of conductivity of the PAn composites during removal of secondary dopant is accompanied by an obvious decrease of ESR signal. (C) 2001 Elsevier Science BN. All rights reserved.