Optical Properties and Photoexcitations in Regularly Alternating Conjugated Copolymers

ABSTRACTWe report in this short paper a preliminary account on the design, preparation, optical characterization and photoexcitation of a class of novel conjugated polymers consisting of regularly alternating thiophene and benzene sequences, which Might represent Models for one-dimensional superlattices. Optical absorption and emission spectra suggest that the barriers produced by the phenylene Moieties do not interrupt the conjugation but can produce localization effects. Resonant Raman spectra indicate that a selective response of the thiophene Moiety occurs upon excitation with visible light. Moreover these Measurements confirm the presence of a confinement on the thiophene blocks, while the biphenil Moiety does not appear to feel the energy barrier and behaves as the corresponding polymer poly (paraphenylene) (PPP). CW photomodulation spectra show that the formation of long-lived bipolarons takes place only if the thienylenic Moiety is long enough to accomodate the lattice distortion.