Poly(vinyl diphenylquinoline): A new pH-tunable light-emitting and charge-transport polymer synthesized by a simple modification of polystyrene

Electroactive and blue light-emitting poly(vinyl diphenylquinoline) (PVQ) was synthesized in nearly quantitative yield by a simple modification of polystyrene. The new polymer and its model compound 2,4-diphenylquinoline were characterized by H-1 NMR, FT-IR, photoluminescence spectroscopies, and thermal analysis. PVQ has a glass transition temperature of 185 degreesC, is soluble in many organic solvents, and is a weak base comparable in basicity to poly(vinylpyridine). It emits blue light in neutral solution and in thin solid films. In acidic solutions, PVQ exhibits a pH-tunable photoluminescence with emission maximum that varies from 486 nm (blue) to 529 mn (green). Intramolecular excimer emission was observed in acidic solutions but not in neutral solutions or thin films of the polymer. The dominant fluorescence lifetimes of the polymer were about 1.2-1.3 ns in thin films or neutral solutions and close to 20 ns in acidic solutions. The coupling of acid-base chemistry to light-emitting and optoelectronic properties in PVQ suggests that it may find applications in electroluminescence, sensors, and catalysis.