An electroluminescent diode using liquid-crystalline conducting polymer

Poly(p-phenylene vinylene) derivatives substituted with a long side chain c ontaining alkoxybiphenyl mesogenic unit have been synthesized and its elect rical and optical properties have been studied. A liquid-crystalline molecu lar alignment and layer structure have been confirmed by optical microscopi c observation and X-ray diffraction measurement, respectively. The dielectr ic constant changes in a stepwise manner at phase transition temperature. T he bandgap of this new polymer in the liquid-crystalline phase has been eva luated to be about 2.3 eV, which monotonously decreases with decreasing tem perature. It has been found that the emission spectra of electroluminescent diode using this new liquid-crystalline polymer as an emissive layer depen d on the polarity of the applied voltage. (C) 2000 Elsevier Science S.A. Al l rights reserved.