STRUCTURAL STUDIES OF POLY(PARA-PHENYLENEAMINE) AND ITS OXIDATION

The structural changes associated with the chemical oxidation of poly(p-phenyleneamine) or “leucoemeraldine” (PLM) were determined quantitatively by X-ray photoelectron spectroscopy (XPS) and qualitatively by infrared (IR) absorption spectroscopy and thermogravimetric analysis (TGA). XPS and IR data showed that some of the amine repeating units of PLM were oxidized slowly by oxygen to the imine structure. Treatment of PLM with 1 M HCl involved a gradual oxidation of the polymer to give rise to a partially protonated emeraldine (PEM). Oxidation of PLM by chlorine resulted in a nitrogenonium ion structure analogous to that arising from the protonation of imine nitrogen in PEM by HCl. However, a substantial amount of the halogen dopant was incorporated into the polymer as covalent chlorine even at low chlorine loading. Oxidative “doping” of PLM by organic electron acceptors such as tetrachloro-o-benzoquinone (o-chloranil) and tetrabromo-o-benzoquinone (o-bromanil) involved first the oxidation of the amine nitrogen and also the formation of the imine structure through hydrogen transfer from the pristine amine nitrogen to the acceptor. The so-produced imine nitrogen was in turn doped by the acceptor. XPS data of the PLM-halobenzoquinone complexes indicated that the nitrogenonium cations of the polymer were balanced by the halogen and the oxygen or benzoquinone anions. © 1990, American Chemical Society. All rights reserved.