Preparation and characterization of electrically conducting copolymers of aniline and anthranilic acid: evidence for self-doping by x-ray photoelectron spectroscopy

Homopolymers and copolymers based on anthranilic acid and aniline have been chemically prepared and characterized by a number of techniques including X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), and differential scanning calorimetry (DSC). The solubility increases while the conductivity decreases with the amount of anthranilic acid in the system. XPS results indicate concurrent self-doping by the -COOH group. The degree of protonation remains at approximately equals 20-30% but the conductivity varies drastically depending on the amount of self-doping versus external doping by HCL. DSC results suggest intramolecular and intermolecular interactions through hydrogen bonding made possible by the -COOH group. These and other results have been rationalized on the basis of the effect of the -COOH substituent on the polymer structure.