Synthesis, magnetic, and optoelectronic properties of poly(triphenylamine-alt-phenylenevinylene)s

Conjugated polymers alternatively involving m-phenylenevinylene or p-phenylenevinylene and a triphenylamine moiety in the main chain were synthesized via a Wittig-Horner-type polycondensation of 4-diformyl-4′,4″-dimethyl-triphenylamine or 4-diformyl-4′,4″-dimethoxy-triphenylamine with m-xylene-bis(diethylphosphonate) or p-xylene-bis(diethylphosphonate). A high glass-transition temperature (ca. 120 °C) and thermal stability (5% weight loss at temperatures greater than 450 °C) were observed for all polymers. These polymers, especially poly(methyltriphenylamine-alt-p-phenylenevinylene), fluoresced a strong green color under UV irradiation, with a quantum efficiency of 50% for their chloroform solutions. Cyclic voltammetry showed a relatively low ionization potential (5.18-5.44 eV) for the polymers. These results suggest that these polymers satisfied the requisites of polymer materials for a single-layer light-emitting diode. The aminium radical derived from the oxidation of poly(triphenylamine-alt-m-phenylenevinylene) satisfied both non-Kekule-type π-conjugation and ferromagnetic connectivity of the unpaired electrons and displayed a multiplet ground state.