Studies of solution properties of polyaniline by membrane osmometry

A series of studies have been carried out on polyaniline (emeraldine base; EB) prepared by polymerization of aniline in aqueous solution, in an effort to determine the molecular weight by the primary method membrane osmometry. The osmotic pressure was determined on various concentrations of EB solutions in the solvent N-methylpyrrolidinone (NMP). The reduced osmotic pressure of polyaniline in NMP was measured, molecular weight determined and a theta temperature determined. The second virial coefficients were calculated. The number average molecular weight of the polymer, determined by membrane osmometry, was found to be approximately 64,000 and the theta temperature 57.7 °C at the reported conditions. Various synthesis conditions and different temperatures were applied for preparation of polyaniline and the number average molecular weights of the polymer were determined. The molecular weight results obtained by membrane osmometry were compared with the molecular weight results obtained by gel permeation chromatography. Both methods showed that the molecular weight strongly depended upon the synthesis conditions. The polymers obtained were characterized by various spectroscopic techniques.