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  • 1
    Electronic Resource
    Electronic Resource
    Polymer light-emitting devices using ionomers as an electron injecting and hole blocking layer (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2128-2134 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of ion concentration, neutralization level and counterions in ionomers was systematically studied to obtain the optimal electroluminescent (EL) characteristics in polymer light-emitting diodes using poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) for the emissive layer and sulfonated polystyrene (SPS) ionomers for the electron-injecting layer. The optimum ion concentration of NaSPS was determined to be at 6.7 mol %. Ionomers with a higher neutralization level make the EL device more efficient, with the highest efficiency being at 200% overneutralization. The ionomer with a smaller metal counter ion greatly enhances the efficiency of EL devices with the indium–tin–oxide/MEH-PPV/LiSPS/Al device having the highest EL quantum efficiency, 1.18% photons/electron. The dominant factor in enhancing the luminance is the number of ionic dipoles near the cathode irrespective of the type of metal counterions, while the hole blocking mostly depends on the restriction of chain segmental motion in ionomers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1391215
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  • 2
    Electronic Resource
    Electronic Resource
    Low-threshold blue amplified spontaneous emission in a statistical copolymer and its blend (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 424-426 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We 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 Förster-type excitation energy transfer, respectively. A single component waveguide made of CPDHFPV gave the threshold energy of 160 nJ/cm2/pulse. Moreover, that of the PVK/CPDHFPV (95/5 by wt.) blend device was as low as 20 nJ/cm2/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. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491297
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  • 3
    Electronic Resource
    Electronic Resource
    High-efficiency polymer light-emitting devices using organic salts: A multilayer structure to improve light-emitting electrochemical cells (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 214-216 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Balanced charge injection in polymer light-emitting devices is very important for high brightness and quantum efficiency. To improve the well-known light-emitting electrochemical cells (LECs), we fabricated multilayer electroluminescent devices employing an ammonium salt-containing poly(ethylene oxide) blend as hole- or electron-injecting materials. The charge injection can be greatly promoted due to the ionic space charges near both electrodes. The current–voltage–optical output characteristics of the triple-layer device using both the hole- and the electron-injecting layers are very similar to the well-known LEC devices. We obtained high quantum efficiencies of 0.9% and 1.5% photons/electron in forward- and reverse-bias field of the triple-layer device, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490635
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of electrical annealing on the luminous efficiency of thermally annealed polymer light-emitting diodes (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3334-3336 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both high brightness and high efficiency of polymer light-emitting diodes can be obtained by electrical annealing after an appropriate thermal treatment. Light-emitting diodes made of poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) with an Al electrode were used for this study. Thermal annealing after Al deposition dramatically enhanced the luminous efficiency of electroluminescent (EL) devices about 230 times at 350 mA/cm2, and the maximum external quantum efficiency (QE) also approached 1.43% photons/electrons. With the bias voltage annealing after thermal annealing, not only the onset voltage of the device was reduced but also the efficiency was further enhanced. This enhanced luminance and efficiency is attributed to the dipoles and accumulated space charges of polar ionic impurities within the MEH-PPV that induce more electronic charges for bipolar recombination. We obtained an external QE of 1.96% photons/electrons after 170 °C thermal annealing and 15 V bias annealing. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1328095
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  • 5
    Electronic Resource
    Electronic Resource
    Improvement of quantum efficiency in polymer light-emitting diodes by a single-ion conductor (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3161-3163 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polymer light-emitting diodes were fabricated using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] as an emissive material. Sodium ionic polyurethane (NaPU), a single-ion conductor (SIC), was employed as an electron-injecting material and compared with the case of sodium sulfonated polystyrene (SSPS). The quantum efficiency was greatly enhanced, compared with the SSPS-based device. The electron injection in the NaPU-based device is more favorable, compared with the SSPS-based device because of a larger ionic space charge accumulation near the cathode by the good chain segmental motion of the soft block in the polymer chains of the SIC. Thus, a balanced injection of an electron–hole pair can be achieved to greatly improve the quantum efficiency. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126616
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular weight distribution and moments for condensation polymerization with variant reaction rate constant depending on chain lengths (1988)
    s.l. : American Chemical Society
    Macromolecules 21 (1988), S. 732-735 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00181a030
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrogenation of poly(vinyl cinnamate) thin layer (1999)
    Springer
    Polymer bulletin 42 (1999), S. 149-152 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Hydrogenation of poly(vinyl cinnamate) was performed with RhH(CO)(PPh3)3 catalyst with intent to clarify the photoalignment mechanism of liquid crystals on poly(vinyl cinnamate) alignment layer. The hydrogenated cinnamate side group shows the characteristic peaks at 2.9 ppm and 2.5 ppm in 1H-NMR spectrum, and a decreasing peak at 280 nm in UV spectrum. This reaction can reveal the role of dimerized or residual cinnamate groups in the applications of the polymeric layer for electronic devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050446
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  • 8
    Electronic Resource
    Electronic Resource
    Miscibility and Biodegradability of Poly(Butylene Succinate)/Poly(Butylene Terephthalate) Blends (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 53-66 
    Details
    ISSN: 1572-8900
    Keywords: Miscibility ; biodegradability ; composting test ; transesterification reaction ; poly(butylene succinate) ; poly(butylene terpehthalate)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract As one of the biodegradable polymers, the blend of poly(butylene succinate) and poly(butylene terephthalate) is dealt with in this study. In our previous work, it was demonstrated that PBS and PBT are immiscible not only from the changes of T g but also from logG′–log G″ plots. It is expected that the biodegradability of the blends could be improved by enhancing the miscibility. We tried to induce the transesterification reaction between two polyesters with various time intervals to enhance the miscibility of the blends. The extent of transesterification reaction was examined by 1H-NMR. We utilized a dynamic mechanical thermal analyzer and a rotational rheometer to investigate the changes in miscibility. We also verified the biodegradability of PBS/PBT blends after the transesterification reaction by the composting method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021846219775
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal characteristics of organoclay and their effects upon the formation of polypropylene/organoclay nanocomposites (2000)
    Springer
    Polymer bulletin 45 (2000), S. 191-198 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary We have examined thermal characteristics of two types of organically modified montmorillonite (OMMT) with different alkylammonium cations and their effects upon the formation of PP nanocomposite, when using a maleic anhydride grafted polypropylene oligomer (maPP) as a compatibilizer. The microstructure of the composite has been characterized by X-ray diffraction (XRD) analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. OMMT showed the decrease of the interlayer spacing at the processing temperature, due to the release of organic ion by thermal decomposition. Thermal characteristics of OMMTs depended greatly on the interlayer structure of OMMT. When the OMMT with small interlayer spacing and less organophilicity was used, PP composite resulted in the only partial exfoliation due to thermal decomposition of the clay layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890070048
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  • 10
    Electronic Resource
    Electronic Resource
    Compatibility of poly(ethylene 2,6-naphthalate) and poly(butylene 2,6-naphthalate) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1807-1810 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends prepared from poly(ethylene 2,6-naphthalate) (PEN) and poly(butylene 2,6-naphthalate) (PBN) show only partial miscibility judged from their glass transition temperatures. Two distinct mechanical behaviors are observed: brittle for the blends 〈 20 wt% of PBN, while ductile 〉 20 wt% of PBN. The experimental modulus and strength values of the blends are within the predicted values according to Kleiner and Paul models, respectively. This means that PEN/PBN blends are somewhat compatible based on their tensile properties. Especially for 20 wt% of PBN blend, the high modulus and strength are observed. The viscosity of the blend is high, which may imply a somewhat entangled morphology in the amorphous state.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352210
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