Chemical, electronic, and structural properties of conducting heterocyclic polymers: A view by XPS

Abstract

XPS techniques have been used to characterize electrically conducting films of polypyrrole and polybithiophenes as grown electrochemically. These techniques have yielded information not only on the nature of the polymeric cation and its counter anion but also on the structural disorder in these polymers. In particular the N1s spectra have revealed a nonuniformity in the distribution of the anions relative to the nitrogen atoms and the C1s spectra clearly show that as many as 1/3 of the pyrrole rings can be different from the rest. Significant improvement in the structural order is achieved by blocking the β sites on the pyrrole ring with methyl groups to ensure a completely α,α′ bonded polymer. Similar experiments on polybithiophene polymers show that this polymer is considerably more ordered than polypyrrole. The XPS results are best interpreted by assigning a nonmetallic character to the pyrrole polymers, in accordance with other experiments.