Synthesis and optoelectronic properties of liquid‐crystalline copolymers based on fluorene and triphenylamine‐containing oligo(p‐phenylenevinylene) derivatives for white light emission

A series of novel liquid‐crystalline copolymers based on fluorene and triphenylamine‐containing oligo(p‐phenylenevinylene) derivatives have been synthesized according to the Suzuki polymerization method. The structures, optical and electrochemical properties of the copolymers were characterized by ¹H NMR, ¹³C NMR, GPC, UV–vis, photoluminescence (PL) spectroscopy, and cyclic voltammetry (CV), respectively. The thermotropic phase behavior of the copolymers was investigated by using differential scanning calorimetry (DSC) and polarized optical microscope (POM). All of the copolymers exhibit thermally liquid crystalline properties and represent the characteristic Schlieren textures in a wide temperature range. The effects of the concentrations and chain length of the oligo(phenylenevinylene) units on the thermal properties, liquid crystalline, photo‐ and electroluminescent properties of the copolymers have been investigated in details. Among the copolymers‐based devices with a configuration of ITO/PEDOT:PSS/polymers/Ca/Al, the device based on PF‐LOPV05 exhibits the lowest turn‐on voltage of 3 V and the maximum brightness of 210 cd/m² at 8.3 V. A single layer device based on the blend of PF/PF‐LOPV05 emits white electroluminescence with CIE coordinates of (0.30, 0.35) at 8 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3296–3308, 2009