Controlled synthesis of high molecular weight polyaniline and poly(o-methoxyaniline)

The molecular weight of polyaniline can be substantially increased from that normally obtained (Mw ≈ 53 000) by the oxidative polymerization of aniline with ammonium peroxydisulfate at about 0 to 3 °C up to about 218 000 by the presence of selected dissolved neutral salts. A further increase up to Mw ≈ 385 000 can be obtained by carrying out the polymerization at about −40 °C. Similar results are obtained for the polymerization of o-methoxyaniline to yield a maximum Mw ≈ 221 000 at 0 to 3 °C and Mw ≈ 417 000 at about −40 °C. The results are consistent with a reduction in the rate of the initiation step in solution and an increase in the rate of the chain propagation step at the solid polymer/solution interface caused by Donnan equilibrium effects.