Photophysical study of two alternating polyfluorene copolymers exhibiting dual fluorescence

We present a photophysical study of two fluorene alternating coporymeis in dilute solutions. The UV-Vis absorption spectra of the copolymers show two absorption bands in the 300-600 nm wavelength range. In spite of the alternating nature of the copolymers the fluorescence spectrum, recorded by excitation within the higher energy absorption band, is also composed of two bands. The excitation spectra show that the lower energy emission band has contributions from both absorption bands, while the picosecond time-resolved fluorescence studies do not provide evidence for any energy transfer process, meaning that, if it occurs, is faster than the time resolution of our set up (≈5 ps).