LOW-TEMPERATURE SYNTHESIS OF HIGH-MOLECULAR-WEIGHT POLYANILINE

Oxidative chemical polymerization of aniline in hydrochloric acid solu tion at sub-zero temperatures leads to polyaniline with a molecular we ight five to ten times higher than that prepared at room temperature. The optimum polymerization temperature to give a polymer with the high est yield and molecular weight has been determined, and solution state C-13 n.m.r. spectroscopy shows that the improved polyaniline has fewe r defect sites compared to the standard polymer. Despite these intrins ic improvements, the conductivity is of the same order of magnitude as standard polyaniline. A solvent-cast film of polyaniline camphorsulfo nate had a conductivity of 295 S cm(-1), although this rose to 820 S c m(-1) along the stretch direction after the film had been uniaxially o riented. An oriented film cast from N-methyl-2-pyrrolidone solution an d protonated with methanesulfonic acid showed a conductivity of 260 S cm(-1) along the stretch direction and 31 S cm(-1) perpendicular to th is. Copyright (C) 1996 Elsevier Science Ltd.