COMPETITIVE DOPING IN HETEROCYCLIC CONDUCTING POLYMERS

The preferential incorporation of perchlorate into the polymer, from e lectrolyte solutions also containing hexafluorphosphate, a phenomenon previously observed during the preparation of polypyrrole, has now bee n shown to take place in substituted derivatives of polypyrrole, polyt hiophene and also in polyazulene. In these ring systems the presence o f electron-donating side groups enhances the effect. Preferment of per chlorate to various degrees is seen in all systems so far studied, inc luding a number of different solvents, and is strongest in solvents of low nucleophilicity, such as nitromethane. Polypyrrole and polythioph ene from acetonitrile solutions that contain only the respective anion s show a higher dopant ratio in perchlorate-containing films compared with hexafluorophosphate films, suggesting that the competitive doping effect between these anions results from preferential perchlorate com pensation of cationic species produced during the polymerisation.