Optical and Magnetic Properties of Polyaniline Derivatives Having Ionic Groups

Copolymers of aniline and sulfonated anilines prepared by electrochemical polymerization show pH-dependent absorption spectra such as for the pure polyaniline, except for the difference in critical pH value of the chromic phenomenon. Dependences of electron spin resonance (ESR) spectra of the copolymers corresponding to the polaronic state on solution pH also suggests that protonation and deprotonation of the nitrogen atom occurs in a pH range different from that of polyaniline, and is attributed to effects of the self-doping of sulfonic acid group in the protonated form. ESR spectra of the copolymers show anomalous temperature dependence which is similar to that of antiferromagnetic material. Copolymers of aniline with sulfonated aminonaphthalenes also exhibit antiferromagnetic behavior.