Influence of polymerization parameters on the molecular weight of polyaniline

The yield of polymerization and the molecular weight of polyaniline (PAN) w ere determined in dependence on the ratio of aniline and amoniumperoxodisul phate, temperature, reaction time and pH. It was found that polymerization yield and molecular weight decrease with the increasing ratio oxidant to an iline, pH and temperature. The pH of the reaction mixture rapidly decreases due to the release of proton from 0.80 to 0.35 and during the polymerizati on slowly increases back to the starting value. The polydispersity is in th e wide range and is almost constant with the changing reaction parameters. After the reduction of emeraldine base to leucoemeraldine base, the molecul ar weight decreases due to the difference in the hydrodinamic volume of qui noid segments in comparision with that of benzenoide, as well as to intermo lecular hydrogen bonds between amine and imine groups of benzenoid and quin oide segments of emeraldine base, and the decomposition of the -C-N- bonds after the reduction.