Electron‐transporting semi‐rigid polyester‐imides made up of a tetracarboxdiimide of p‐terphenyl analogue of 1,3,4‐oxadiazole: Preparation, and thermal, optical, and electrochemical properties

Abstract

AbstractElectron‐transporting semi‐rigid polyester‐imides composed of a tetracarboxdiimide (2,5‐di(3,4‐dicarboxphthalimido)‐1,3,4‐oxadiazole; DDPOD) of p‐terphenyl analogue of 1,3,4‐oxadiazole were successfully prepared by the melt polycondensation of a monomer, a dialcohol derivative of DDPOD, with four diesters in the presence of zinc acetate as a catalyst, and their thermal, UV–vis absorption, photoluminescent (PL) and electrochemical properties were examined. The structures of the resulting polymers were characterized by Fourier transform infrared and 1H NMR spectroscopies and elemental analyses. Differential scanning calorimetry measurements, X‐ray diffraction analyses and polarizing microscope observations suggested that the polymers prepared from aliphatic diesters formed highly ordered thermotropic liquid crystalline smectic phases. The UV–vis and PL spectra in the solutions and in the films displayed that the obtained polymers showed absorption and bluish violet‐light emissions based on the DDPOD moiety. Cyclic voltammetry measurements revealed that these polymers had more stable HOMO levels and were more sensitive to oxidation than polymers comprising electron‐accepting 2,5‐diphenyl‐1,3,4‐oxadiazole in the backbones. The DDPOD unit brought the extension of differences between electron‐injection and hole‐injection barriers in the polymers. It was found that the polymers containing the DDPOD unit in the main chains in this study not only showed bluish violet light‐emitting properties but also behaved as electron‐transporting materials for organic electroluminescent devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012