Photoluminescent, Liquid-Crystalline, and Electrochemical Properties of Para-Phenylene-Based Alternating Conjugated Copolymers

Novel liquid-crystalline alternating conjugated copolymers [P(P(6)CN-alt-Cz) and P(P(6)CN-alt-MeP)] with phenylene and carbazolylene or phenylene with methyl substitution onto the main chain have been synthesized through palladium-catalyzed Suzuki coupling reactions. The influence of the incorporation of carbazolylene and the substituted phenylene into the main chain on the thermal, mesomorphic, and luminescent properties has been investigated by Fourier transform infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet-visible spectroscopy, photoluminescence (PL), and cyclic voltammetry. These polymers show highly thermal stability, losing little of their weights when heated to 360 degrees C. The conjugated copolymers exhibit liquid crystallinity at elevated temperature. The existence of the chromophoric terphenyl core endows the copolymers with high PL and the polymer P(P(6)CN-alt-Cz containing carbazolylene unit can emit more pure blue light. All the copolymer films with low band gaps about 2.3-2.4 eV undergo reversible oxidation and reduction processes, significantly lower than the band gap of poly(p-phenylene). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 434-442, 2010