Purification and characterisation of poly(2-methoxyaniline-5-sulfonicacid acid)

The chemical oxidative synthesis of water soluble sulfonated polyaniline, poly (2-methoxy aniline-5-sulfonic acid) (PMAS) has been shown to result in an impure mixture of polymeric isomers. A tangential cross flow dialysis system has been developed to rapidly and efficiently separate high molecular weight polymer from low molecular weight oligomers, and results compared to conventional tubing dialysis. Characterisation of the purified polymer fractions has been made using UV-vis spectroscopy, gel permeation chromatography, cyclic voltammetry, conductivity measurement and thermal analysis. Results indicate that while the conventional dialysis tubing is not able to separate the mixture of high and low molecular weight materials efficiently, the cross flow dialysis is able to separate them more rapidly and efficiently. Purified high molecular weight PMAS exhibited enhanced electrical conductivity and significant property changes with respect to tubing dialysed PMAS. The pure PMAS, which is the high molecular weight species (Mw 10157 Da) obtained from the cross flow dialysis, has a twofold higher conductivity than the impure PMAS dialysed by the conventional method.