Novel fluorene-pyridine-based alternating copolymers: syntheis, characterization and optical properties

A novel series of well-defined soluble poly[2,7-(9,9-dialkyfluorenyl)-alt-pyridinyl] (except for PDHFP-25, a polymer with same composition but different weight-average molecular mass (Mw) was reported in reference [B. Liu, W.L. Yu, Y.H. Lai, W. Huang, Chem. Mater. 13 (2001), 1984-1991] were synthesized using palladium-catalyzed Suzuki cross-coupling reactions in good to high yields. In the series of alternating copolymers, 2,7-(9,9-dialkylfluorenyl) was used as the light emitting unit and the electron deficient pyridinyl unit was employed to provide improved electron transportation. All these polymers were characterized by 1H NMR, 13C NMR, GPC, thermal analyses, UV-vis and fluorescence spectroscopy. The shorter pendant 9,9-dihexyl at fluorenyl unit is better to polymer for higher thermal stability and higher Tg than 9,9-dioctyl at fluorenyl unit. The meta-linkage (3,5- or 2,6-linkage) of pyridinyl units in the polymer backbone is more favourable to polymer for pure blue emission and prevention of aggregation of polymer chain than the para-linkage (2,5-linkage) of the pyridinyl units.