ポリ(p-フェニレンビニレン)誘導体のサーモクロミズム

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We have investigated on the thermochromic behaviors of poly (p-phenylene vinykene) derivatives, poly (2, 5-dialkoxy p-phenylene vinylene) s, ROPPVs and poly (2, 5-dialkyl p-phenylene vinylene), RPPV. The temperature dependence of optical properties such as optical absorption and photoluminescence spectra and the variation of properties with the side chain length have been compared with those of poly (3-alkylthiophene) s, PATs. The bandgap energy of ROPPV increases gradually from 2.2 eV at room temperature to about 2.4 eV at 200℃, but that of RPPV does not depend on temperature and shows a nearly constant value of about 2.7 eV. The temperature dependence of bandgap energy is different from those of PATs and the difference can be tentatively interpreted in terms of the main chain structure. The photoluminescence intensities decrease monotonically with increasing temperature. We speculate on the separation of the excited species due to the reduction of distance between polymer main chains and the enhancement of the overlap of π-electrons with the twist of polymer main chains. Moreover, we have evaluated the electronic states of ROPPVs and RPPVs at the solid and liquid states from the measurement of ionization potentials.
2007-02-28