1,720,981 research outputs found
Effect of dialcohols on properties of poly(ethylene 2,6-naphthalate) copolymers
No full textProperties of poly(ethylene 2,6-naphthalate) (PEN) and its copolymers containing diethylene glycol (DEG), propanediol (PD), butanediol (BD), and bisphenol A ethoxylate (BSA) were investigated. The copolymer composition was determined by H-1-NMR spectroscopy. It has a higher value than the feed composition due to the high volatility of ethylene glycol (EG). The melting temperature of the copolymers was gradually depressed with the increase of dialcohol in the composition. The complex viscosity of the copolymers did not depend on the molecular weight, but on the chemical structure. The complex viscosity of the copolymers containing 3 mol % of DEG, ED, and 5 mol % of ED was lower than that of PEN, and the mechanical properties were similar with the value of PEN. (C) 1999 John Wiley & Sons, Inc
Low-threshold blue amplified spontaneous emission in a statistical copolymer and its blend
No full textWe report low-threshold, blue amplified spontaneous emission (ASE) in a statistical copolymer, poly(9,9-dihexylfluorene-2,7-divinylene-m-phenylenevinylene-stat-p-phenylenevinylene) (CPDHFPV) and its blend with poly(9-vinylcarbazole) (PVK). PVK and CPDHFPV acted as the donor and the acceptor of the Forster-type excitation energy transfer, respectively. A single component waveguide made of CPDHFPV gave the threshold energy of 160 nJ/cm(2)/pulse. Moreover, that of the PVK/CPDHFPV (95/5 by wt.) blend device was as low as 20 nJ/cm(2)/pulse. From the relationship between the ASE intensity and the film thickness, we suggest that the optimum thickness for the photopumped ASE should be the transverse electric-mode cutoff thickness. (C) 2002 American Institute of Physics
A Reliability-Based Capacity Rating of Existing Bridges by Incoperating System Identification
No full textLow-threshold amplified spontaneous emission in a fluorene-based liquid crystalline polymer blend
No full textWhite emission from a polymer blend light-emitting diode by incomplete cascade energy transfer
No full textWhite light emission was obtained from a polymer light-emitting diode (LED) made of a ternary polymer blend comprised of poly(9-vinylcarbazole) (PVK), poly(9,9'-dihexlyfluorene-2,7-divinylene-m-phenylenevinylene-stat-p-phenylenevinylene) (CPDHFPV), and poly[2-methoxy-5-(2'-(ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) (19:1:1 by wt.). Incomplete cascade energy transfer was employed to obtain white emission from the polymer blend LED. Compatibility between PVK and CPDHFPV facilitated the Forster-type energy transfer from PVK to CPDHFPV. However, poor compatibility between CPDHFPV and MEH-PPV resulted in a partial energy transfer between the polymers causing the blend to emit two colors simultaneously. Consequently, pure white color near CIE coordinate (0.33, 0.33) could be obtained with a low sensitivity to the drive voltage
Cascade energy transfer in dye-doped ternary polymer blend light-emitting diodes
No full textWe report the realization of efficient and color-variable organic electroluminescent (EL) devices which employ the cascade energy transfer in a dye-doped ternary polymer blend. Fluorene-based light-emitting polymers, poly(2,7-bis(p-stiryl)-9,9'-di-n-hexylfluorene sebacate) (PBSDHFS) and poly(9,9'-di-n-hexylfluorenediylvinylene-alt-1,4-phenylenevinylene) (PDHFPPV), and a laser dye, DCM were used for this study. Forster excitation energy transfer in the PBSDHFS/PDHFPPV (98w/2w), PDHFPPV/DCM (98w/2w), PBSDHFS/DCM (98w/2w), and PBSDHFS/PDHFPPV/DCM (98w/2w/2w) blend played an essential role in achieving color-tunability as well as high efficiency due to the reduced self-absorption loss and concentration quenching. The EL device made of the PBSDHFS/PDHFPPV/DCM (98w/2w/2w) blend showed the highest EL quantum efficiency (QE). We attribute this result to an effective carrier trapping capability of DCM as well as the excitation energy transfer. (C) 2002 Elsevier Science B.V. All rights reserved
Cascade Excitation Energy Transfer in Polymer Blend for Light-emitting Diodes and Lasers
No full textLasing actions from a liquid crystalline polymer blend
No full textWe report lasing actions from fluorene-based copolymer blends with liquid crystallinity in waveguide geometry. Fluorene-based light emitting polymers, poly[2,7-bis(p-stiryl)9,9 ' -di-n-hexylfluorene sebacate] (PBSDHFS) and poly(9,9 ' -di-n-hexyl fluorenediylvinylene-alt-1,4-phenylenevinylene) (PDHFPPV), and a laser dye, 4(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) were used in this study. We employed Forster type energy transfer from a liquid crystalline donor to a non-crystalline acceptor to tune the color and obtain low threshold for gain narrowing. We obtained a low-threshold energy (similar to 20 nJ/cm(2) per pulse) for gain narrowing of PBSDHFS/PDHFPPV (98:2, by wt.) blend film. PBSDEFS/PDHFPPV/DCM (99:2:2, by wt.) blend film possesses a threshold energy of similar to 14 muJ/cm(2) per pulse, while the PDHFPPV/DCM blend film did not per pulse. Forster excitation energy transfer played the most show gain narrowing even at a pump energy as high as 12 mJ/cm(2) important role in improving the performance of lasing actions and tuning the output colours. (C) 2001 Elsevier Science B.V. All rights reserved
SYNTHESIS AND CHARACTERIZATION OF NOVEL SIDE-CHAIN NONLINEAR-OPTICAL POLYMERS BASED ON POLY(1,6-HEPTADIYNE) DERIVATIVES
No full textNovel types of multifunctional polymer that contain a conjugated backbone for both third- and second-order nonlinear optical (NLO) materials have been investigated. We synthesized the 1,6-heptadiyne derivatives bearing NLO chromophores. The resulting monomers were easily homopolymerized and also copolymerized with ethyl dipropargyl(diethoxyphosphoryl)acetate (TDPA) using a metathesis catalyst to give corresponding polymers with large optical nonlinearities. Molecular structural characterizations for the resulting polymers were achieved by H-1- and C-13-NMR, FTIR, and UV-visible spectroscopies. The polymers obtained were found to be amorphous and showed thermal stability up to 250 degrees C. The homogeneous polymer solutions could be spin coated to the optical quality thin films on the ITO glass substrates. These films have been oriented by an electric contact poling process. The electrooptic coefficients, r(33), of the poled polymer films were in the range 1.7-10.1 pm/V, and the nonresonant values of the third-order NLO coefficient, chi((3)), were found to be (2.1-3.3) x 10(-11) esu
White Emission from a Polymer Blend Light-Emitting Diode by Incomplete Cascade Energy Transfer
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