CONTROLLED SYNTHESIS OF HIGH-MOLECULAR-WEIGHT POLYANILINE AND POLY(O-METHOXYANILINE)

The molecular weight of polyaniline can be substantially increased from that normally obtained ((M) over bar(w) approximate to 53 000) by the oxidative polymerization of aniline with ammonium peroxydisulfate at about 0 to 3 degrees C up to about 218 000 by the presence of selected dissolved neutral salts. A further increase up to (M) over bar(w) approximate to 385 000 can be obtained by carrying out the polymerization at about -40 degrees C. Similar results are obtained for the polymerization of o-methoxyaniline to yield a maximum (M) over bar(w) approximate to 221 000 at 0 to 3 degrees C and (M) over bar(w) approximate to 417 000 at about -40 degrees 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.