STRUCTURAL INVESTIGATIONS OF AROMATIC AMINE POLYMERS

The polymerization of p-phenylenediamine, diphenylamine, phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, and N,N'-diphenylbenzidine by either Cu(ClO4)2-6H2O in acetonitrile or (NH4)2S2O8 in dilute HClO4 or HCl was investigated. Elemental analysis, thermogravimetric analysis, infrared and ultraviolet-visible absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to elucidate the chemical structures of the resulting products. The degree of polymerization and the protonation behavior depend on both the monomer and the polymerization method. In general, of the rive aromatic amines studied, the polymers from phenyl-p-phenylenodiamine and N,N'-diphenyl-p-phenylenediamine are found to be more similar to polyaniline. The polymerization of diphenylamine proceeds via phenyl-phenyl coupling in the para positions, while the polymer from p-phenylenodiamine consists of N-N couplings in addition to the C-N bonds. The degree of polymerization of N,N'-diphenylbenzidine is very low. The XPS results show that in the as-synthesized salts, protonation may occur at either the imine or amine units depending on the monomer used. The aromatic amine polymers are susceptible to forming covalent bonds with chlorine when HCI is used as the protonic acid during synthesis.