Polymers of phenylenediamines

The chemical or electrochemical oxidation of phenylenediamines in acidic aqueous media yields the corresponding oligomers or polymers. Their structures and properties are discussed in relation to a closely-related conducting polymer, polyaniline. Depending on the reaction conditions, polyphenylenediamines are produced as powders, colloidal dispersions, thin films, or composites. In contrast to polyaniline, polyphenylenediamines are rated as non-conductors and their conductivities are low. Similarly to polyaniline, these polymers display a salt-base transition and they are redox-active. They act as reductants of noble-metal compounds to the corresponding metals or as precursors in the carbonization to nitrogen-rich carbons. Applications proposed in the literature are outlined; they include the corrosion protection of metals, catalysis, electrorheology, sensors, energy-conversion devices, electrochromism, noble-metal recovery, and water treatment.