Photoinduced intramolecular charge separation at the repetition units of light-emitting alternating copolymers

Light-emitting nitrogen-containing poly(phenylene vinylene) PPV-related copolymers are synthesized by the well-known Wittig-Homer reaction. The alternating copolymers have hole-transporting moieties such as triphenylamine (TPA) and conjugated aromatic units such as 1,4-phenylene, 1,4- or 1,5-naphthylene and 9,-10-anthrylene. The dipole moments within the repetition units of the copolymers in the excited state are estimated by measuring the solvent effect on absorption and fluorescence emission spectra, indicating that charge separation is present, The dipole moment values are in agreement with the electron affinities of acceptors, i.e., aromatic units. The evidence can help to elucidate the photophysical behavior, particularly the fluorescence quantum efficiencies.