The effect of added water on the conformation of optically active polyaniline in organic solvents

Dissolution of emeraldine base (EB) into organic solvents (NMP, DMSO, DMF, DMPU) and doping with 0.1 M (1S)- (+)-10-camphorsulfonic acid (HCSA) forms optically active PAn.(+)-HCSA emeraldine salts. The addition of small amounts of water (1 to 10% v/v) to the organic solvents prior to acid doping has a striking effect upon the conformation of the resultant emeraldine salts. Marked changes in the intensity of their circular dichroism spectra occur, and in some cases an inversion of configuration is observed. The addition of 25-50% water to the EB/organic solvent mixtures prior to doping with (+)-HCSA leads to optically inactive emeraldine salts. In contrast, the addition of water to optically active PAn.(+)-HCSA after formation via acid doping in organic solvents has no significant effect upon their chiroptical properties.