Blue organic light-emitting devices with an oxadiazole-containing emitting layer exhibiting excited state intramolecular proton transfer

We report a blue organic light-emitting device having an emissive layer of 2-(2-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole (HOXD), that exhibits excited state intramolecular proton transfer (ESIPT). The device had a luminance efficiency of 0.8 cd/A and a maximum brightness of 870 cd/m(2). Electroluminescence spectra revealed a dominating peak at 450 nm and two additional peaks at 480 and 515 nm with a full width at half maximum of 50 nm. Our studies indicate that some EL may originate from the triplet excitation state of the enol form of HOXD.

New PPV oligomers containing 8-substituted quinoline for light-emitting diodes

Two new poly(phenylenevinylene) (PPV) oligomers, 2,2'-(1,4-phenylenedivinylene)bis-8-acetoxy quinolines were synthesized via a Knoevenagel condensation reaction. The single-crystal X-ray diffraction study shows that there are intermolecular pi...pi interactions in the solid state of 2,2'(1,4-phenylenedivinylene)bis-8-acetoxyquinoline. Electroluminescent properties using these compounds as emitters have been investigated.

Synthesis and properties of optically active polyquinolines containing 1, 1 '-binaphthyl unit

Optically active 2,2'-dimethoxy-6,6'-diacetyl-1,1'-binaphthyl (DMDABN) was prepared from 2,2'-dimethoxy-1,1'-binaphthyl, and its structure was comfirmed by elemental analysis, NRM, IR and MS. Optically active polyquinolines were synthesized with DMDABN and 4,4'-diamino-3,3'-dibenzoyldiphenyl ether by Friedlander reaction. These polyquinolines showed high glass transition temperatures (474-578 K), high decomposition temperatures (703-770 K), insolubility in many common organic solvents and strong chiral activity.

Novel blue light-emitting PPV-based copolymer containing triazole and carbazole units

A novel alternating conjugated copolymer containing triazole and carbazole units was synthesized by the Wittig reaction. The resulting bipolar conjugated polymer emits a pure light with good thermal stability, which is a promising candidate for polymer light emitting display.

Liquid crystalline and light emitting polyacetylenes: Synthesis and properties of biphenyl-containing poly(1-alkynes) with different functional bridges and spacer lengths

Biphenyl- (Biph-) containing 1-alkynes (3 and 4) and their polymers (1 and 2) with varying bridge groups and spacer lengths were synthesized and the effects of the structural variation on their properties, especially their mesomorphism and photoluminescence behaviors, were studied. The acetylene monomers 3(3) [HCdropC(CH2)(3)O-Biph-OCO(CH2)(10)CH3] and 4(m) [HCdropC(CH2)(m)OCO-Biph-OCO(CH2)(10)-CH3, m = 3, 4] were prepared by sequential etherization and esterification reactions of 1-alkynes. While 3(3) exhibits enantiotropic crystal E and SmB mesophases, its structural cousin 4(3) displays only a monotropic SmB phase. Enantiotropic SmA and SmB mesophases are, however, developed when the spacer length is increased to 4. Polymerizations of the monomers are effected by Mo-, W-, Rh-, and Fe-based catalysts, with the WCl6-Ph4Sn catalyst giving the best results (isolation yield up to 85% and M-w up to 59000). The polymers were characterized by IR, UV, NMR, TGA, DSC, POM, XRD, and PL analyses. Compared to 1(3), 2(3) shows a red-shifted absorption, a higher T-i, and a better packed interdigitated bilayer SmA(d) structure, while the mesophase of 2(4) involves monolayer-packing arrangements of the mesogens. Upon photoexcitation, 1(3) emits almost no light but 2(m) gives a strong ultraviolet emission (lambda(max) similar to 350 nm), whose intensity increases with the spacer length.

Crystal structure and variation in unit cell parameters with crystallization temperatures of poly (ether ketone ether ketone ketone)s containing meta-phenyl links (PEKEKmK)

The X-ray diffraction patterns of the crystalline aromatic ketone polymer PEKEKmK (aryl ether ketone ether ketone ketone polymer containing meta-phenyl links) have been investigated (for the chemical structure, see Formula). An orthorhombic unit cell is proposed to contain two chains with a = 0.772 nm, b = 0.604 nm and c = 2.572 nm. According to the orthorhombic system, the 11 reflections of this polymer were indexed. Meanwhile, variation in unit cell parameters with crystallization temperatures of PEKEKmK was also investigated. [GRAPHICS]

Synthesis of C-1 bridge-containing metallocene catalysts and their catalytic activities for olefin polymerization

The synthesis and characterization of metallocene complexes which can be used as catalysts in the presence of MAO for olefin polymerization were discussed in the present paper. The metallocene complexes have been characterized by IR, H-1 NMR, EI-MS spectra and element analyses; The catalytic features of Olefin polymerization were studied under different conditions. Metallocenes in which metals is Ti had no activity for ethylene polymerization, Polymers with different features can be obtained by using different catalysts.

Networks with hexagonal circuits in co-ordination polymers of metal ions (Zn-II, Cd-II) with 1,1 '-(1,4-butanediyl)bis(imidazole)

Three new compounds, [ZnL1.5(H2O)(SO4)]. 6H(2)O 1, [ZnL1.5(H2O)(2)][NO3](2). 2H(2)O 2 and [CdL1.5(H2O)(2)(SO4)]. 4H(2)O 3 were obtained from self-assembly of the corresponding metal salts with 1,1'-(1,4-butanediyl)bis(imidazole) (L). In both 1 and 2 zinc ion is five-co-ordinated, showing a less-common trigonal bipyramidal co-ordination polyhedron, while cadmium ion of 3 is six-co-ordinated with a common octahedral arrangement. The sulfate ions of 1 and 3 are co-ordinated, however the nitrate ions of 2 are not. Each of the three compounds is composed of a (6, 3) network with the hexagonal smallest circuit containing six metal ions and six L; each L is co-ordinated to two metal ions, acting as a bridging ligand. In 1 the 2-D sheet of (6, 3) networks is interpenetrated in an inclined mode by symmetry related, identical sheets to give an interlocked 3-D structure, while the (6, 3) networks of both 2 and 3 stack in a parallel fashion to construct frameworks having channels.

Synthesis and properties of three novel series of monomers containing para-methoxyazobenzene as the mesogenic group

Three novel series of monomers, namely n-1-bromo-[4-(4-methoxyphenylazo)phenyloxy]-alkanes (Bn, n = 3, 6, 10), n-[4-(4-methoxyphenylazo) phenyloxy]alkyloxy-4-methoxybenzene (Cn, n = 3, 6, 10) and n-[4-(4-methoxyphenylazo)phenyloxyl]alkyloxy-[4-methoxy-2,5-bis-(chloromethyl)] benzene (Dn, n = 3, 6, 10) were synthesized and characterized with FTIR, H-1 NMR, UV-visible and fluorescence spectroscopy. Their thermal behaviour was studied by different scanning calorimetry and polarizing optical microscopy. The results show that B3, B6 and C6 exhibit monotropic nematic liquid crystalline behaviour.

Crystallization behavior of a novel ether ketone polymer containing meta-phenylene linkage: PEKEKK (T/I)

Nonisothermal and isothermal melt crystallization kinetics of a novel aryl ether ketone polymer containing meta-phenylene linkages, PEKEKK (T/I), were studied by differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny and a new approach by combining the Avrami equation with the Ozawa equation could describe the nonisothermal crystallization. Isothermal crystallization could also be described by the Avrami equation. The activation energies were 187 and 159 kJ/mol for nonisothermal and isothermal crystallization, respectively. Using the Hoffman-Weeks method, the equilibrium melting point T-m(o) was estimated as 353 degrees C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter K-g of the isothermal melt crystallization was estimated as 5.49 x 10(5) K-2. The crystallization characteristics of PEKEKK (T/I) were compared with those of all-para PEKEKK. The differences were explained by differences in the chain flexibility of the two polymers.

Synthesis and characterization of novel bipolar PPV-based copolymer containing triazole and carbazole units

Two new blue light-emitting PPV-based conjugated copolymers containing both an electron-withdrawing unit (triazole-TAZ) and electron-rich moieties (carbazole-CAR and bicarbazole-BCAR) were prepared by Wittig condensation polymerization between the triazole diphosphonium salt and the corresponding dialdehyde monomers. Their structures and properties were characterized by FT-IR, TGA, DSC, UV-Vis, PL spectroscopy and electrochemical measurements. The resulting copolymers are soluble in common organic solvents and thermally stable with a T-g of 147degreesC for TAZ-CAR-PPV and of 157degreesC for TAZ-BCAR-PPV. The maximum photoluminescence wavelengths of TAZ-CAR-PPV and TAZ-BCAR-PPV film appear at 460 nm and 480 nm, respectively. Cyclic voltammetry measurement demonstrates that TAZ-BCAR-PPV has good electrochemical reversibility, while TAZ-CAR-PPV exhibits the irreversible redox process. The triazole unit was found to be an effective pi-conjugation interrupter and can play the rigid spacer role in determining the emission colour of the resulting copolymer.

Fabrication of layer-by-layer deposited multilayer films containing DNA and its interaction with methyl green

Multilayer films were fabricated by layer-by-layer electrostatic deposition techniques between poly(diallyIdimethylammonium chloride) (PDDA) and calf thymus DNA (CT DNA) on glassy carbon and quartz substrates. Electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy demonstrated the uniform assembly of PDDA/DNA multilayer films, and X-ray photoelectron spectroscopy confirmed the elemental composition of the films. Moreover, the interaction of DNA in PDDA/DNA films with methyl green was investigated by UV-vis spectroscopy and circular dichroism (CD). (C) 2001 Elsevier Science B.V. All rights reserved.

Simple preparation method of multilayer polymer films containing Pd nanoparticles

A simple route to the fabrication of multilayer films containing Pd nanoparticles is described. Following layer-by-layer assembly of PdCl42- and polycation, QPVP-Os (a quaternized poly(4-vinylpyridine) complexed with [Os(bpy)(2)Cl](2+/+)), on 4-aminobenzoic acid-modified glassy carbon electrodes, the three-dimensional Pd nanoparticle multilayer films are directly formed on electrode surfaces via electrochemical reduction of PdCl42- sandwiched between polymers. The growth of PdCl42- is easy on electrode surfaces by electrostatic interaction, and the assembly processes are monitored by cyclic voltammetry and UV-vis spectroscopy. The depth profile analyses by X-ray photoelectron spectroscopy verify the constant composition of the Pd nanoparticle multilayer films. Atomic force microscopy proves that the as-prepared Pd nanoparticles are uniformly distributed with an average particle diameter of 3-7 mn. The resulting Pd nanoparticle multilayer-modified electrode possesses high catalytic activity for the reduction of dissolved oxygen and oxidation of hydrazine compounds in aqueous solution.

Synthesis and characterization of novel sodium sulfonate-functionalized poly(ether ether ketone)s containing cyclohexyl side groups

Novel water insoluble sodium sulfonate-functionalized poly(ether ether ketone)s containing cyclohexylidene in the main chain with degree of sulfonation up to 2.0 were synthesized from nucleophilic polycondensation of 5, 5'-carbonylbis (2-fluorobenzenesulfonate), 4, 4'-difluorobenzophenone and 4, 4'-cyclohexylidenebisphenol. The polymers showed excellent thermal stability and good water resistance as well. The DSC diagrams and WAXD patterns indicated an amorphous morphological structure of these polymers. A comprison of some properties between these copolymers and polymers derived from bisphenol A was given.