Poly[2,7-(9,9-dihexylfluorene)-alt-pyridine] with donor-acceptor architectures: A new series of blue-light-emitting alternating copolymers

A novel series of well-defined alternating poly[2,7-(9,9-dihexylfluorenyl)-alt-pyridinyl] (PDHFP) with donor-acceptor repeat units were synthesized using palladium (0)-catalyzed Suzuki cross-coupling reactions in good to high yields. In this series of alternating polymers, 2, 7-(9,9-dihexylfluorenyl) was used as the light emitting unit, and the electron deficient pyridinyl unit was employed to provide improved electron transportation. These polymers were characterized by 1 H-NMR and 13 C-NMR, gel permeation chromatography (GPC), thermal analyses, and UV-vis and fluorescence spectroscopy. The glass transition temperature of copolymers in nitrogen ranged from 110 to 148 °C, and the copolymers showed high thermal stabilities with high decomposition temperatures in the range of 350 to 390 °C in air. The difference in linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases. Meta-linkage (3,5- and 2,6-linkage) of pyridinyl units in the polymer backbone is more favorable to polymer for pure blue emission and prevention of aggregation of polymer chain than para-linkage (2,5-linkage) of the pyridinyl units.