Preparation and characteristics of nonflammable polyimide materials

The thermal and flame-retardant properties of homo- and copolyimides were evaluated. Those containing sulfone linkages in the backbone were found to be more flame retardant. Both properties were dependent on the composition. A polyimide/silica nanocomposite was obtained through sol-gel processing. The effects of the addition of silica an the dispersion, interfacial adhesion, fire resistance, mechanical properties, and thermal stability of the composites were investigated. SEM analysis showed a good dispersion of silica with a diameter of 50-300 nm in the organic matrices. The addition of silica increased the fire retardancy and mechanical properties of the composites. (C) 2000 John Wiley & Sons, Inc.

White Electroluminescence from a Star-Like Polymer with an Orange Emissive Core and Four Blue Emissive Arms

A star-like white light-emitting polymer with an orange emissive core and four blue emissive arms is designed and synthesized. White electroluminescence is observed with simultaneous orange emission from the core and blue emission from the arms. A single-layer device based on this polymer emits white light with CIE coordinates of (0.35, 0.39) and a luminous efficiency of 7.06 cd A(-1).

Blue electroluminescent polymers with dopant-host systems and molecular dispersion features: polyfluorene as the deep blue host and 1,8-naphthalimide derivative units as the light blue dopants

We developed a series of highly efficient blue electroluminescent polymers with dopant-host systems and molecular dispersion features by selecting 1,8-naphthalimide derivatives as the light blue emissive dopant units, choosing polyfluorene as the deep blue emissive polymer host and covalently attaching the dopant units to the side chain of the polymer host. The polymers' EL spectra exhibited both deep blue emission from the polymer host and light blue emission from the dopant units because of the energy transfer and charge trapping from the polymer host to the dopant units.

Phosphonate-Functionalized Polyfluorene as a Highly Water-Soluble Iron(III) Chemosensor

An anionic, phosphonate-functionalized polyfluorene, i.e., poly(9,9-bis(3'-phosphatepropyl)fluorene-alt-1,4-phenylene) sodium salt (PFPNa), has been synthesized by copolymerization of phosphonic acid-substituted 2,7-dibromofluorene and phenyldiboronic ester via direct Suzuki polycondensation reaction in DMF/water. Polymer PFPNa is highly soluble and emissive in water with a solubility of 60 mg/mL and a photoluminescence quantum yield of 75%. The absorption and fluorescence spectra of PFPNa are strongly dependent on pH value owing to the partial protonation of phosphate groups and the aggregation of the polymer chains.

Improving performance of polymer photovoltaic devices using an annealing-free approach via construction of ordered aggregates in solution

Low crystalline order has been proved to be one of the main hindrances for achieving high performance devices based on thin films composed of crystallizable polymer. In this work, we use a facile method to substantially improve crystallinity of poly(3-hexylthiophene) (P3HT) in its pure or composite film via the construction of ordered precursors in the solution used for thin film deposition. These improvements have been confirmed by bright-field transmission electron micrography, electron diffraction, UV-Vis absorption and wide-angle X-ray diffraction.

White light emission on amplified spontaneous emission with dye content controlled polymer system

White light emission from amplified spontaneous emission (ASE) was realized by optically pumping fluorescent dye 4-(dicy-anomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped semiconducting poly(9,9-dioctylfluorene) (PFO) polymer thin films. Two individual ASE peaks originating from DCJTB and PFO were observed by carefully controlling the DCJTB concentration in PFO. The studies of the ASE characteristics of DCJTB:PFO thin films lead to the conclusion that the DCJTB:PFO system with 0.3% w/w DCJTB dopant concentration in PFO showed the best ASE performance.

Band Gap Tunable, Donor-Acceptor-Donor Charge-Transfer Heteroquinoid-Based Chromophores: Near Infrared Photoluminescence and Electroluminescence

A series of D-pi-A-pi-D type of near-infrared (NIR) fluorescent compounds based on benzobis(thia diazole) and its selenium analogues were synthesized and fully characterized by H-1 and C-13 NMR, high-resolution mass spectrometry, and elemental analysis. The absorption fluorescence, and electrochemical properties were also studied. Photoluminescence of these chromophores ranges from 900 to 1600 nm and their band gaps are between 1.19 and 0.56 eV.

Near-infrared polymer light-emitting diodes based on infrared dye doped poly(N-vinylcarbazole) film

Infrared light-emitting diodes possess potential applications in optical communication and safety detection. in this paper, we fabricated near-infrared light-emitting diodes possess potential applications in optical communication and safety detection. in this paper, we fabricated near-infrared polymer light-emitting diode employing a commercial near-infrared (NIR) organic dye as an emissive dopant dispersed within poly(N-vinylcarbazole) (PVK) by spin-casting method. The used device structure was indium tin oxide/3,4-polyethylene-dioxythiophene-polystyrene sulfonate/PVK: NIR dye/Al.

Synthesis and characterization of phenylene-thiophene all-conjugated diblock copolymers

Grignard metathesis (GRIM) polymerization for all-conjugated diblock copolymers comprising poly (2,5-dihexyloxy-1,4-phenylene) (PPP) and poly(3-hexylthiophene) (P3HT) blocks were systematically studied with LiCl as additive and 1,2-bis (diphenylphosphino) ethane nickel dichloride (Ni(dppe)Cl-2) or 1,3-bis(diphenylphosphino) propane nickel dichloride (Ni(dppp)Cl-2) as catalyst. It was found that the addition order of the monomers was crucial for the success of copolymerization. With the monomer addition in the order of phenyl and then thienyl Grignard reagents, all-conjugated PPP-b-P3HT diblock copolymers with different block ratios were successfully synthesized. In contrast, the inverted addition order only afforded a mixture containing both block copolymers and deactivated or end-capped homopolymers.

Synthesis and Characterizations of Poly(9,10-bisarylethynyl-2,6-anthrylene)s and Poly(9,10-bisalkynyl-2,6-anthrylene)

A poly(9,10-bisalkynyl-2,6-anthrylene) (PI) and five poly(9,10-bisarylethynyl-2,6-anthrylene)s(P2-P6) as soluble conjugated polymers have been synthesized and characterized. All polymers exhibit two-dimensional conjugated characteristics as indicated by absorption spectra comprising multi-bands in the range of 300-600 nm. Compared with P1, polymers P2-P5, which contain phenylethynyl substituents with the longer conjugation than alkynyl groups, exhibit a similar to 60 nm red shift of absorption edge. However, further increasing the conjugation length of the arylethynyl substituents (longer than phenylethynyl) has only a no effect on the conjugation of the polymer chains, while comparing the absorption spectra of P6 with those of P2-P5.

Poly(oligothiophene-alt-benzothiadiazole)s: Tuning the Structures of Oligothlophene Units toward High-Mobility "Black" Conjugated Polymers

A series of donor-acceptor low-bandgap conjugated polymers, i.e., PTnBT (n = 2-6), composed of alternating oligothiophene (OTh) and 2,1,3-benzothiadiazole (BT) units were synthesized by Stille cross-coupling polymerization. The number of thiophene rings in OTh units, that is n, was tuned from 2 to 6. All these polymers display two absorption bands in both solutions and films with absorption maxima depending on n. From solution to film, absorption spectra of the polymers exhibit a noticeable red shift. Both high- and low-energy absorption bands or P'F5BT and PT6BT films locate in the visible region, which are at 468 and 662 nm for PT5BT and 494 and 657 nm for PT6BT.

Novel spiro-fluorenes from tandem radical addition for liquid crystalline monodisperse conjugated oligomers

3'-Nonafluorobutylmethyl-4'-methyl-spiro[cyclopentyl-9,1']fluorenes were successfully synthesized via tandem radical-addition reactions between 9,9-diallylfluorenes and perfluorobutyl iodide in the presence of a radical initiator followed by reduction under mild conditions. Single crystal analysis indicates that two substituents at 3,4-positions of cyclopentane are in a maleinoid form. Accordingly, four oligo(fluorene-co-bithiophene)s with the same molecular length of similar to 10 nm (7 fluorene units and 12 thiophene units) containing one to three novel spiro-fluorene units were synthesized.

Solution-Processable Carbazole-Based Conjugated Dendritic Hosts for Power-Efficient Blue-Electrophosphorescent Devices

A novel class of hosts suitable for solution processing has been developed based on a conjugated dendritic scaffold. By increasing the dendron generation, the highest occupied molecular orbital (HOMO) energy level can be tuned to facilitate hole injection, while the triplet energy remains at a high level, sufficient to host high-energy-triplet emitters. A power-efficient blue-electrophosphorescent device based on H2 (see figure) is presented.

Controlled phase separation for efficient energy conversion in dye/polymer blend bulk heterojunction photovoltaic cells

Low-cost photovoltaic energy conversion using conjugated polymers has achieved great improvement due to the invention of organic bulk heterojunction. in which the nanoscale phase separation of electron donor and acceptor favors realizing efficient charge separation and collection. We investigated the polymer photovoltaic cells using N, N'-bis(1-ethylpropyl)-3,4,9,10-perylene bis(tetracarboxyl diimide)/poly(3-hexyl thiophene) blend as an active layer. It is found that processing conditions for the blend films have major effects on its morphology and hence the energy conversion efficiency of the resulting devices. By optimizing the processing conditions, the sizes of donor/acceptor phase separation can be adjusted for realizing efficient charge separation and collection. The overall energy conversion efficiency of the photovoltaic cell processed with optimized conditions increases by nearly 40% compared to the normally spin-coated and annealed cell.