Excitation energy transfer in a cationic water-soluble conjugated co-polymer studied by time resolved anisotropy and fluorescence dynamics

The excitation energy transfer in a new water-soluble poly(fluorenevinylene-co-phenylenevinylene) is investigated by time resolved anisotropy and fluorescence dynamics. This is realized in concentrated aqueous and EtOH solutions using femtosecond time resolved upconversion spectroscopy. At short emission wavelengths, the anisotropy dynamics indicate a single depolarization mechanism attributed to the reorientation of isolated chains. At long emission wavelengths, two depolarization mechanisms are observed. The fast one, occurring within 10-20 ps, is ascribed to interchain energy transfer, while the slow one is attributed to reorientation of isolated and aggregated chains. Isotropic fluorescence dynamics also reveal a fast decay mechanism supporting the energy transfer conclusion.