New luminescent 1,2,4-triazole/thiophene alternating copolymers: Synthesis, characterization, and optical properties

New five-membered ring heteroaromatic copolymers composed of 1-alkyl-1H-1,2,4-triazole and thiophene or bithiophene units were prepared by palladium-catalyzed polycondensation. The copolymers were soluble in organic solvents, and showed number-average molecular weights of 6200-23,700 in the GPC analysis. NMR spectroscopy revealed that the copolymers had a regio-random molecular structure. The optical properties, as well as the electrochemical properties, of the copolymers in solutions and films were determined. The polymers exhibited blue photoluminescence (PL) with an emission peak at about 420 nm and quantum yields of 36-43% in solutions, and the PL peak shifted to 470-480 nm in films. X-ray diffraction data suggested that the polymers formed a π-stacked structure in solid state.