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

A novel series of poly(2,5-dialkoxy-1,4-phenylene-alt-2,5-pyridine)s functionalized 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 thermal 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 consistent with the rigid-rod conjugated structure. They emitted intense blue light under UV irradiation in both the film and solution phases with high quantum yields. Singlelayer blue light-emitting diodes were successfully fabricated using these materials as emitting layers. The electrochemical behavior of these new polymers depicted facile n-doping and good electron transporting properties attributable to the presence of the electron-withdrawing pyridinyl unit. These polymers displayed bathochromic shift when protonated with trifluoroacetic acid in chloroform solutions. The surface morphologies of the polymer films cast from chloroform and chloroform/trifloroacetic acid mixtures were investigated by scanning electron micrographs.