New electroluminescent alternating polyfluorenevinylenes with phenylene and biphenylene segments

The Heck coupling of 9,9-dihexyl-2,7-divinylfluorene with 1,4-dibromobenzene and 4,4′-dibromobiphenyl afforded the alternating polyfluorenevinylenes P1 and P2, respectively. P2 showed lower solubility in common organic solvents, higher thermal stability and slightly higher glass transition temperature than P1. The polymers absorbed around 400 nm, and their optical band gaps were 2.77–2.82 eV. They emitted blue-green light in both solution (emission maximum 451–464 nm, quantum yield 0.52–0.54) and thin film (emission maximum 462–474 nm).