Novel efficient blue fluorescent polymers comprising alternating phenylenepyridine repeat units: Their syntheses, characterization, and optical properties

A novel series of poly(2,5-dialkoxy-1,4-phenylene-alt-2,5-pyridine)s functi onalized with alternating donor/acceptor repeat units was synthesized using a Suzuki coupling approach and characterized by FT-IR, NMR (C-13 and H-1), UV-vis, fluorescence spectroscopy, gel permeation chromatography, and ther mal analyses. The derived polymers were soluble in common organic solvents and trifloroacetic acid and exhibited good thermal stability. In all cases, the electronic and optical properties of these novel copolymers were consi stent with the rigid-rod conjugated structure. They emitted intense blue li ght under UV irradiation in both the film and solution phases with high qua ntum yields. Singlelayer blue light-emitting diodes were successfully fabri cated using these materials as emitting layers. The electrochemical behavio r of these new polymers depicted facile n-doping and good electron transpor ting properties attributable to the presence of the electron-withdrawing py ridinyl unit. These polymers displayed bathochromic shift when protonated w ith trifluoroacetic acid in chloroform solutions. The surface morphologies of the polymer films cast from chloroform and chloroform/trifloroacetic aci d mixtures were investigated by scanning electron micrographs.