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81.
Wei Song Marvin D. Rausch James C. W. Chien 《Journal of polymer science. Part A, Polymer chemistry》1996,34(14):2945-2953
The effect of reaction conditions, including catalyst concentration, temperature, and immobilization on support, have been investigated for syndioselective propylene polymerization by the “bare” zirconocenium ion generated from 1,1-diphenyl-methylidene(1-η5-cyclopentadienyl)(9-η5-fluorenyl)zirconium-dichloride precursor (2). Neither variation of the catalyst concentration nor immobilization of 2 on silica support affect the syndiospecificity of polymerization. The stereoregularity of the syndiotactic polypropylene, as judged from the melting transition temperature and homosteric r-pentad population by 13C-NMR, were found to be proportional to polymer molecular weight. These behaviors are compared with a typical isoselective catalyst ethylenebis(4,5,6,7-tetrahydroindenyl) Zr precursor (4). They are in close resemblance in the case of the S-enantiomeric complex of 4, but the racemic mixture of 4 is markedly inferior. The origins of stereo- and regio-errors are discussed. © 1996 John Wiley & Sons, Inc. 相似文献
82.
Reagen Ying‐Tai Su Li‐Ko Chiu Shan‐Wei Weng Ying‐Shiun Chou Raymond Chien‐Chao Tsiang 《Journal of Polymer Science.Polymer Physics》2012,50(4):280-288
White polymeric light‐emitting diode (WPLED) based on a single polymer, poly(3‐hexylthiophene‐alt‐9,9‐dioctylfluorene) (PTAF), has been successfully demonstrated. This conjugated alternating copolymer, PTAF, comprises 50 mol % of 3‐hexylthiophene which is an orange‐red color chromophore and 50 mol % 9,9‐dioctylfluorene which is a bluish‐green color chromophore. It was synthesized by Suzuki cross‐coupling reaction and has a molecular weight of 15,021 and polydispersity of 1.36. Nanocomposite consisting PTAF and graphene nanosheets enhances the optoelectronic properties and the device fabricated with a configuration of ITO/PEDOT:PSS/(PTAF + 1% graphene)/Ca/Al shows two‐color white electroluminescence with CIE 1931 coordinates of (0.28, 0.34). The white luminescence from a single polymer affords the WPLED device a simple structure and low fabrication cost. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
83.
84.
Nguyen Van Hieu Nguyen Van Duy Pham Thanh Huy Nguyen Duc Chien 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2950-2958
Nb-Pt co-doped TiO2 and the hybrid SWCNTs/Nb-Pt co-doped TiO2 thin films have been prepared by the sol–gel spin-coating process for gas-sensor fabrication. Field emission scanning electron microscope (FE-SEM, TEM and X-ray diffraction (XRD) characterizations indicated that the SWCNTs inclusion did not affect the morphology of the TiO2 thin film and the particle size. Additionally, the SWCNTs were well embedded in the TiO2 matrix. The gas-sensing properties of Nb–Pt co-doped TiO2 thin films with and without SWCNTs inclusion were investigated. The hybrid sensors with the inclusion of different SWCNTs contents are examined to elucidate the effect of SWCNTs content on the gas-sensing properties. Experimental results revealed that the responses to ethanol of Nb–Pt co-doped TiO2 sensors with SWNCTs inclusion increase by factors of 2–5 depending on the operating temperature and the ethanol concentration, compared to that of the sensor without SWCNTs inclusion. Moreover, all hybrid sensors can operate with high sensitivity and stability at a relatively low operating temperature (<335 °C). The responses of the hybrid sensors are greatly affected by SWCNTs content inclusion. The optimized SWCNTs content of 0.01% by weight was obtained for our experiment. The improved gas-sensing performance should be attributed to the additional formation of the p/n junction between SWCNTs (p-type) and TiO2 (n-type). 相似文献
85.
Rhodium nanoparticles dispersed by a CO2 microemulsion are effective catalysts for rapid hydrogenation of arenes in supercritical CO2. 相似文献
86.
James C. W. Chien 《Journal of polymer science. Part A, Polymer chemistry》1968,6(2):375-379
Polyethylene hydroperoxide (PEH) was prepared by low-temperature autoxidation initiated by AIBN. Over 85% of the total hydroperoxyl groups decompose by a rapid process, the remainder dissociate at about one-tenth of that rate. The results are the same whether PEH is decomposed in solution or in the solid state. Large amounts of scavenger have no effect on these decompositions; there is no radical-induced processes. The results suggest mechanisms of decomposition involving neighboring group assistance. 相似文献
87.
88.
The Curie temperatures (TC) and the hyperfine interactions of amorphous Fe40Ni40PyB20?y(0≤y>≤20) have been determined by 57Fe Mössbauer spectroscopy. In this series of amorphous solid with a fixed transition-metal content, the metalloid atoms are shown to have a noticeable effect on TC, isomer shift and hyperfine field distribution. 相似文献
89.
Room temperature Mössbauer and its r.f. induced sideband effects are studied in glassy Fe40Ni40P14B6 and Fe80P16C3B1 alloys in ribbon forms. The direction of the magnetic anisotropy is found to be in the plane of the ribbon for the first alloy while the latter has some out-of-plane anisotropy component. The 3d electronic configuration for iron in the two alloys seems to be about the same in light of the observed isomer shifts and the electron donor model. The r.f. induced sidebands in the spectra are attributed to the magnetostriction of the present alloys. 相似文献
90.
B. Barnett D. Blockus M. Burka C. Y. Chien D. Christian W. Koska L. Madansky C. May Y. T. Oh A. Pevsner S. Wagner C. Woody N. C. Yang 《Physics letters. [Part B]》1983,120(4-6)
Results are presented from a search for a ρ0ρ0 enhancement in antiproton annihilations. A ρ0ρ0 resonance was recently observed in radiative ψ decays, and its existence has been supported by the results of an antiproton experiment at 5.7 GeV/c. No indication of this ρ0ρ0 enhancement is seen is our data, in direct contradiction with the earlier, lower statistics experiment. 相似文献