Spectroscopic properties of poly(1,4-phenylenevinylene) and poly(2-methoxy-1,4-phenylenevinylene)

The spectroscopic properties of poly(1,4-phenylene vinylene) [PPV] and poly(2-methoxy -1,4-phenylene vinylene) [PMPV] in thin film were investigated with FT-IR, UV-VIS absorption, and photoluminescence. From FT-IR and polarized luminescence spectra of stretched films, we found that luminescences in PPV and PMPV were mainly due to the decay of an intra-chain exciton. Through the temperature dependent photoluminescence spectra, we found that the weakening f the exciton-phonon interaction on cooling results in the fluorescence linewidth narrowing, and there exists a thermally activated barrier in excited state potential well. The origins of the bathochromic shift of emission line on cooling are discussed.