Absolute Molecular Weight of Polyaniline

The absolute molecular weight of polyaniline in the pernigraniline, emeraldine, and leucoemeraldine oxidation states has been measured by light scattering and the exact number of aniline repeat units determined for the first time. Using potential-time profiling to monitor the chemical oxidative polymerization of aniline using ammonium peroxydisulfate oxidant, all three oxidation states of polyaniline can be synthesized in one step and the evolution of polymer molecular weight monitored. The pernigraniline intermediate formed during the chemical oxidative polymerization of aniline increases by 17−20% when it is converted to emeraldine, which is consistent with a two-step polymerization mechanism. These findings establish a solid experimental framework to chemically synthesize block copolymers of polyaniline by using different monomers to intercept the reaction at the pernigraniline oxidation state.