Polyaniline: conformational changes induced in solution by variation of solvent and doping level

The reduced viscosity of mixtures of polyaniline (emeraldine base, EB) and d,l-camphorsulfonic acid (HCSA) in solutions of m-cresol or chloroform (or in mixtures of these solvents) was investigated. Viscosity measurements as a function of (a) increasing m-cresol content in the mixed solvent for a fully protonated ‘EBH+/CSA−’ polymer, and (b) increasing protonation level of EB by increasing amounts of HCSA in m-cresol, indicate that the fully protonated polymer adopts a maximized expanded molecular conformation in a good solvent such as m-cresol. These results suggest that the greatly different conductivities obtained for ‘EBH+/CSA−’ films cast from m-cresol or chloroform solutions result primarily from their different molecular conformations in these solvents.