Synthesis and optical properties of oligo- and poly(2,5-dialkoxy-1,4-para-phenylenevinylene)s

Model compounds based on 1,4-distyrylbenzene and its 2,5-dialkoxy derivatives were synthesized by the Wittig and Wittig-Horner methods. Corresponding poly(2,5-dialkoxy-1,4-para-phenylenevinylene)s (DAPPVs) were obtained from their 2,5-bis(chloromethyl)benzene monomers. The photophysical behavior of the model compounds and DAPPVs was investigated through absorbance, excitation and fluorescence spectroscopy. The absorbance and fluorescence spectra of DAPPVs are red shifted in comparison to the corresponding three- and five-ring model compounds by 4600 and 7000 cm(-1), respectively. We also report the fluorescence excitation and emission spectra of the model compounds deposited as solid films on quartz and as solid solutions in poly(methyl methacrylate) (PMMA). The photophysical properties of these materials are interpreted from their capacity to form excimer-like molecular dimers. The fluorescence excitation spectra of DAPPV solutions are concentration dependent. We show evidence for the existence of fluorescent aggregates in the solid state.