Solutions and solution-cast films of conducting polymers

When O/M <0.2 and D/M < 1.0, PPy obtained was partially soluble in m-cresol or NMP. Its solubility decreases as the increase of O/M. When O/M was greater than 0.2, the polymer obtained was totally insoluble in any solvent. The solubility of PPy is not determined solely by its molecular weight. Conductivity, inherent viscosity, and ESR data indicate that the solubility is determined by the molecular weight, oxidation state, and degree of crosslinking. UV-Vis spectra of PPy solution in m-cresol and in NMP were quite different from those of the corresponding solid. The sharp peak at 475 nm and the broad peak at 440 nm correspond to π→π* transitions of the neutral and doped forms, respectively, while the peak absorption at 933 nm (1.33 eV) arises from the transition between defect states. PPy film cast from NMP showed very low conductivity (~10−10 S/cm) while the film cast from m-cresol showed 1.310−4 S/cm.