Poly-p-phenylene Phosphine/Polyaniline Alternating Copolymers: Electronic Delocalization through Phosphorus

Abstract

Phosphorus-containing poly(N-arylaniline)s and related polymer model compounds have been prepared. The spectroscopic and electronic properties of the materials were investigated via UV-vis-NIR spectroscopy and cyclic voltammetry. PPPP-PANI copolymers containing p-phenylene diamine units in the polymer backbone have electronic and spectroscopic properties characteristic of aromatic substituted p-phenylene diamines. Copolymers containing -(-C(6)H(4)-P-C(6)H(4)-P-C(6)H(4)-)- linkages between nitrogen centers show evidence for weak electronic delocalization along the polymer chain. The electrochemical and spectroscopic properties support strong electronic delocalization in copolymers containing -(-P-C(6)H(4)-N-C(6)H(4)-)- repeat units. The presence of a single diphenylphosphine bridge between nitrogen centers provides an efficient mode of electronic delocalization between nitrogen centers. PPPP oxide-PANI copolymers and related polymer model compounds were also prepared and investigated. The resemblance of PPPP oxide-PANI copolymers to isolated p-phenylene diamines or triarylamines suggests electronic isolation of the amine fragments in the polymer. The conversion of phosphorus(III) phosphines to phosphorus(V) phosphine oxides inhibits electronic delocalization through phosphorus, further supporting delocalization of the lone pair of electrons on phosphorus in PPPP-PANI copolymers. PPPP-PANI copolymers are a new type of pi-conjugated polymer with low oxidation potentials and electronic delocalization through phosphorus along the polymer chain.