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Fluorescent hyperbranched copolymers (HB-x, x 1⁄4 1–4) with inherent tetraphenylthiophene, triphenylamine (TPA) and quinoline (Qu) moieties were prepared to study the influence of the TPA branching point on the thermal and the spectral stability. All the HB-x copolymers exhibited high glass transition temperatures (Tgs 1⁄4 245–315 C) with the detected values increasing with the increasing branching TPA content in the HB-x. The solid HB-x films possess high emission efficiency with the resulting quantum yields (UFs) in the ranges of 0.72– 0.74. More importantly, the HB-x copolymers and the derived light-emitting devices exhibit high photoluminescence (PL) and electroluminescence (EL) stability towards thermal annealing at temperatures higher than 200 C. After annealing at 200 C (or 300 C), no change was observed in the respective PL and EL spectra of HB-1 (or HB-4) copolymers. The spectral stability was found to correlate with Tg and with the highest branching density, HB-4 copolymer possesses the highest thermal stability among all HB-xs and show no EL spectral change after annealing at 300 C for 4 h. The results indicate that all the branched HB-x copolymers are promising candidates for the polymer light-emitting diodes due to their high quantum yield and spectral stability. VC 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 237–249, 2012

In this study, fluorescent alternative copolymer poly(fluorene-alt-1,6-naphthol) (PFN) with inherent hydroxyl (OH) groups was blended with poly(vinyl pyrrolidone) (PVR) through facile hydrogen-bond (H-bond) interactions. The emission intensities of the resultant PFN/PVR mixtures of different compositions were shown to increase with increasing PVR content in both the chloroform solution and in the solid film states. The H-bond interactions between PFN and PVR resulted in the restricted molecular rotations of the fluorophores, which lead to the blockage of nonradiative energy decay channels and the accompanied emission enhancement. With the efficient H-bond interactions, the PFN/PVR blend with the low content (2.33 wt %) of fluorescent PFN component actually has a high quantum efficiency of 0.93, comparatively higher than other blends containing higher fluorescent PFN. The role of the H-bonding on the restricted molecular rotations of the PFN/PVR blends was therefore evaluated by the infrared, the 1H NMR sp...

A hydrophobic tetraphenylthiophene (TP) center with novel aggregation-induced emission (AIE) property was chemically linked to two poly(N-isoprppylacrylamide) (PNIPAM) chains to obtain thermoresponsive polymers to study the relationships between the lower critical solution transitions (LCSTs) and the AIE-operative fluorenscence (FL) emission. Three ethynyl-terminated PNIPAMs with different molecular weights were synthesized via controlled atom transfer radical polymerization (ATRP) using ethynyl-functionalized initiator. The PNIPAMs were then coupled with diazide-funtionalized TP (TPN3) via click reaction to obtain the desired TP-embedded polymers of Px (x = 1, 2, and 3). All three polymers show AIE-property from their solution fluorescence behavior in THF/hexane mixtures. In the aqueous solution, the TP-center served as a fluorogenic probe that reveals the LCSTs of polymers and its relation to the degree of TP labeling in terms of polymer concentration. The thermoresponsiveness of Px was demonstrated by ...

In this study, fluorescent organic compound FN and polymer PFN with alternative fluorene and naphthol units were prepared to assess the influence of the hydrogen bonds (H-bonds) on the emission behavior. Both FN and PFN exhibit the enhanced aggregation emission behavior with enhanced emissions on solution mixtures of higher degree of aggregation. For solid FN and PFN films, the fractions of the H-bonded hydroxyl groups decrease upon being heated to high temperature, which results in aggregate dissociation and reductions in the aggregation emissions. Meanwhile, procedures leading to the increase of the H-bonds (such as shearing or enhanced aggregation by addition of nonsolvent in the solution preparative step) resulted in solid films with higher emission intensity. Variations on the H-bonds can be detected by infrared spectroscopy and are in line with the emission behavior.

Fluorescent alternative copolymers containing tetraphenylthiophene-quinoline (TP-Qu) moiety were synthesized from Friedlander reaction between o-aminoketone and acetyl groups. With the wholly aromatic-quinoline chain structure, the alternative donor–acceptor copolymers of PTPQu and PTPTPQu are rigid materials with high glass transitions (Tg = 245 and 295 °C, respectively) and with high thermal stability (with ≤2% weight loss at 500 °C). The multiple phenyl pendant rings inherited PTPQu and PTPTPQu copolymers with good solubility in common organic solvents, which facilitate the easy fabrications of light-emitting diode (LED) devices. CV study resulted in the reversible Eox/onset values of 0.78 and 0.75 V for the PTPQu and PTPTPQu copolymers, respectively. With high quantum yields (ϕFs, = 0.59 for PTPQu and 0.74 for PTPTPQu) in the film states, the two copolymers and their devices exhibit stable photoluminescence (PL) and electroluminescence (EL) spectra, respectively, on change of annealing temperatures to at least higher than 250 °C. After annealing at 250 °C (or 300 °C), no change was observed in the respective PL and EL spectra of PTPQu (or PTPTPQu) copolymers. The results indicate that alternative copolymers containing donor–acceptor TP-Qu unit are promising candidates for LEDs with high efficiency and spectral stability. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

In this study, poly[2-(4′-vinylphenyl)-3,4,5-triphenylthiophene] (PTP) with pendant tetraphenylthiophene (TP) groups was synthesized to study its aggregation-induced emission (AIE) property. The solution emission spectra of the PTP nanoaggregates contain discernible monomer and aggregate bands with their relative intensity dependent on the extent of aggregation. Increasing solution concentration or nonsolvent content resulted in the increase of the aggregate to monomer emission ratio. In addition, the aggregate to monomer emission ratio decreases when the PTP film was heated across the glass transition temperature (165 °C). Single-chain conformation of PTP was simulated to probe for the possible arrangements of the pendant TP fluorophores in the isolated (monomer) and the aggregate domains.

In this study, we reported the first example of enhanced photoluminescent (PL) emission by complexing bulky camphorsulfonic acid (CSA) to organic and polymeric materials containing quinoline moiety. Small-molecule 2,4-diphenylquinoline (DPQ) and poly(vinyl 2,4-enylquinoline) (PVQ) were prepared primarily and complexed with equivalent amounts of CSA to generate the DPQ-CSA and PVQ-CSA complexes, respectively. All samples show the character of aggregation-induced emission (AIE); however, DPQ-CSA and PVQ-CSA complexes have higher emission intensities than their respective precursors of DPQ and PVQ. The CSA-complexation tends to hamper the molecular rotations and leads to the observed emission enhancement.

Two novel luminescent boron compounds, BPh2(2-(2-quinolyl)naphtho[b]imidazolato) (1) and BPh2(2-(2-quinolyl)benzimidazolato) (2), have been synthesized by the reactions of triphenylboron with appropriate ligands, 2-(2-quinolyl)naphtho[b]imidazole (QNI) and 2-(2-quinolyl)benzimidazole (QBI), respectively. The structure of 1 was determined by single crystal X-ray diffraction, while 2 by spectroscopic methods. The structure of 1 reveals that the boron center is four coordinated. Several types of OLED possessing different colors were fabricated by using 1 as emitter. For the three-layer OLED with the structure ITO/NPB/2/Alq3/Mg–Ag, an emission band covering the whole visible region from 400 to 750 nm with the maximum brightness of 320 cd/m2 was observed, indicating a perfect white light OLED (CIE = 0.33, 0.37). Compounds 1 and 2 form a new family of organometallic emitting materials which could be of interest for practical application.

A novel chelating ligand, 2-(2-pyridyl)naphtho[b]imidazole (PNI) has been synthesized and structurally characterized. The PNI molecule reacts readily with BPh3 and BF3 to form BPh2(2-(2-pyridyl)naphtho[b]imidazole) (1) and BF2(2-(2-pyridyl)naphtho[b]imidazole) (2), respectively. The structures of PNI and 1 were determined by single crystal X-ray diffraction, while that 2 by spectroscopic methods. The structure of 1 reveals that the boron center is four-coordinated. The electroluminescent device using 1 as the emitting layer shows bright yellow luminescence with a maximum emission peak at 540 nm. Complexes 1 and 2 form a new family of organometallic emitting materials which could be of interest for practical applications.