CONTROL OF CHROMOPHORE LENGTH IN ELECTROLUMINESCENT POLYMERS .2. MAINCHAIN POLYMERS

Electroluminescence emission has been demonstrated in mainchain polyes ters and a structurally analogous polyamide. High molecular weight pol yesters were synthesized by condensation of a dihydroxy functionalized , substituted, phenylene vinylene analogue, e.g., the lumophore, with a variety of dicarboxylic acid chlorides. The structure and hence the conjugation length of the emitting comonomer was predetermined prior t o polymerization. Since the diacid moieties did not contribute to the conjugation length and hence the emission wavelength, the structure of the diacid was determined on the basis of its ease of synthesis, reac tivity, and solubilizing ability in the final polymer. In each of the polyesters the electroluminescence wavelength of light-emitting diodes made from these polymers was similar to their photoluminescence emiss ion spectrum in solution and the solid state at room temperature. The emission wavelengths ranged from blue to green. The polyamide exhibits a very broad band, nearly white electroluminescence. Diodes made from these polymers typically have external efficiencies less than or equa l to 0.003% with low turn-on voltages, e.g., 6-20 V.