Polymer 3 based on 1-(4-hexyloxy)-benzene and 2,4,6-triphenyl-1,3,5-triazine functionalized fluorene units was synthesized and characterized, whose optoelectronic properties were further compared with those of poly(9,9-dihexyl-fluorene) (1) and poly(9,9-di(1-(4-hexyloxy)-phenyl)-fluorene) (2). The 5% weight loss temperatures of polymers 1, 2 and 3 thin solid powders are 274, 318 and 401℃, and their glass transition temperatures in the same state are 91, 120 and 139℃, respectively. The maximum absorption and photoluminescent emission peaks of polymers 1, 2 and 3 in toluene solution are 380 and 435 nm, and their optical band gaps in toluene solution are 2.95, 2.95 and 2.91 eV. The triplet energy levels of polymers 1, 2 and 3 are 2.82, 2.81 and 2.97 eV, while their singlet energy levels are 3.14, 3.13 and 3.12 eV, which makes the singlet-triplet energy splitting gaps for polymers 1, 2 and 3 to be 0.32, 0.32 and 0.15 eV. The highest occupied molecular orbital energy levels of polymers 1, 2 and 3 are -5.72, -5.95 and -5.96 eV and the lowest unoccupied molecular orbital energy levels are -2.70, -2.39 and -2.34 eV. The introduction of 4-hexoxybenzene widened the energy band gaps of the polymers, while the electron deficient 2,4,6-triphenyl-1,3,5-triazine made the single-triplet energy splitting gaps of the polymers successively decreased, but it did not endow polymer 3 with thermally activated delayed fluorescence characteristic. With the introduction of rigid and electron deficient 2,4,6-triphenyl-1,3,5-triazine into the 9-carbon of the fluorene units in the polymer, the thermal stability, color purity and photostability of blue light emitting solid were improved in the turn of polymers 1, 2 and 3, which were further validated by the stable electroluminescent spectra of polymer 3. The wide-angle X-ray diffraction results of the polymers 1, 2 and 3 powders show that all polymers have excellent amorphous properties in nature. The phase diversity of polymer 3 powder locates between those of polymers 1 and 2, and the alkoxyl phenyl substituted group on the polymer 2 side chain is helpful to improve the diversity of ordered morphology in solid powder. The random copolymer 3 exhibits much better photoelectric properties than those of polymers 1 and 2.

Key words: polyfluorene, blue light, pendant group, 2,4,6-triphenyl-1,3,5-triazine, photo physics, thermal stability