XPS studies of copolymers of pyrrole and N-methylpyrrole

Abstract

A series of copolymers as well as the homopolymers based on pyrrole and N-methylpyrrole have been prepared. These polymers were oxidized with bromine during chemical polymerization. The conductivity results show a decreasing order with increasing proportion of N-methylpyrrole in the copolymer. As most of these polymers are insoluble, XPS was used to examine further the role of the bromine oxidant in terms of the amount incorporated and its interaction with the polymer. The results indicate a direct correlation between conductivity and the amount of positively-charged nitrogen along the polymer chain. Not all the bromine dopants are available for oxidation of the nitrogen because of ring substitution. Around 20 - 23% of the total bromine is incorporated as covalent bromide, regardless of the copolymer composition. There is, however, strong evidence to suggest that a higher bromide ion content is found in the more conducting polymers to account for the more extensive oxidation of the nitrogen. © 1989.