Structural study of polyaniline films in reprotonation/deprotonation cycles

Abstract

The structures of emeraldine base films, cast from N-methylpyrrolidinone solution, after being subjected to varying levels of reprotonation and repeated reprotonation/deprotonation are studied using X-ray photoelectron spectroscopy and infrared absorption spectroscopy. Two acids, HCl and HClO4, have been tested, and the results indicate that with the latter the amine units of the film can be protonated much more readily than those of the powder sample. For highly protonated films structural modifications resulting in a higher intrinsic oxidation state are apparent after one reprotonation/deprotonation cycle. The structural modifications have also resulted in the solubility of the films being drastically reduced. By the third reprotonation cycle, the interactions of the anions with the then structurally modified polymer films have resulted in chlorine species of distinctly different nature from those of the first two cycles. In contrast, the powder samples after three reprotonation/ deprotonation cycles show no significant deviation from the pristine base. © 1991 American Chemical Society.