ON THE MORPHOLOGY AND GROWTH OF ELECTROCHEMICALLY POLYMERIZED POLYPYRROLE

Samples of polypyrrole p-toluene sulfonate have been prepared by electrochemical polymerization from aqueous and methanolic solutions. The morphology and molecular ordering have been studied by scanning and transmission electron microscopy, polarizing optical microscopy and wide-angle X-ray scattering. Specimens prepared from aqueous solution develop as compact films, which exhibit considerable molecular anisotropy; cross-sections are highly birefringent and the local molecular orientation is found to correlate with the nodular surface features. Transmission electron microscopy also reveals evidence of supermolecular ordering within the films, which is consistent with the optical observations. Samples prepared from methanolic solutions appear very different: no evidence of molecular anisotropy or internal subdivision has been observed. These films are massively voided as a result of extensive internal delamination, which occurs after the polypyrrole is deposited onto the work electrode. On the basis of the observed morphologies, modes of growth are proposed, based upon polymerization in solution followed by a degree of further chain development after precipitation.