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排序方式： 共有8798条查询结果，搜索用时 15 毫秒
941.
Pramod Kumar Hegde A. Vasudeva Adhikari M. G. Manjunatha C. S. Suchand Sandeep Reji Philip 《应用聚合物科学杂志》2010,117(5):2641-2650
Three new donor–acceptor type poly{2,2l‐(3,4‐ dialkoxythiophene‐2,5‐diyl)bis[5‐(2‐thienyl)‐1,3,4‐oxadiazole]}s ( P1, P2, and P3 ) were synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge‐transporting properties of the polymers were investigated by UV‐visible, fluorescence emission spectroscopic and cyclic voltammetric studies. The polymers showed bluish‐green fluorescence in solutions. The electrochemical band gaps were determined to be 2.03, 2.09, and 2.17 eV for P1 , P2, and P3, respectively. The nonlinear optical properties of new polymers were investigated at 532 nm using single beam Z‐scan and degenerate four‐wave mixing (DFWM) techniques with nanosecond laser pulses. The polymers exhibited strong optical limiting behavior due to “effective” three‐photon absorption. Values of the effective three‐photon absorption ( 3PA ) coefficients, third‐order nonlinear susceptibilities (χ(3)), and figures (F) of merit were calculated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
942.
The electrical properties of a poly(p‐phenylene vinylene) (PPV) conjugated polymer using silver (Ag) as a cathode were improved by the incorporation of silicon dioxide (SiO2) nanoparticles. The current density of the Ag–PPV/SiO2 nanocomposite system was higher than that of Ag–PPV. A lower level of interfacial oxidation was found in the Ag–PPV/SiO2 nanocomposite than in Ag–PPV, confirming that a more complete elimination of residue occurred in the nanocomposite. This was due to the relatively large surface area of the PPV/SiO2 nanocomposite film and the hydrophilic surface of the SiO2 nanoparticles. The lower level of oxidation contributed to an improvement in the material's current–voltage characteristics. Morphology‐dependent current–voltage characteristics were enhanced by a large variation in the thickness of the Ag–PPV/SiO2 nanocomposite film because an increased effective field strength could be induced in the thinner regions of the film. The incorporation of SiO2 nanoparticles altered the effective film thickness and the amount of residue in the interior of the PPV without disrupting the structure of the conjugated polymer. The Ag cathode created a stable interface with the PPV film layer without causing the formation of an organic–metal complex, which would have obstructed electron injection. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
943.
The copolymerization of butadiene (Bd) and isoprene (Ip) with a supported titanium‐triisobutyl aluminum catalyst system was studied. An analysis using differential scanning calorimetry, X‐ray diffraction, and 13C‐NMR spectra indicated that products with 25–60 mol % Bd units were random copolymers and that the melting temperatures and glass‐transition temperatures (Tg) were 30–40 and ?74°C (or thereabout), respectively, which were very similar to those of natural rubber. The chemical structure of these copolymers was characterized by a high‐trans 1,4‐configuration: the trans 1,4‐content of Ip units was greater than 98%, and the trans 1,4‐content of Bd units was greater than 90%. The reactivity ratio of Bd was greater than that of Ip (rBd = 5.7 and rIp = 0.17). The sequence distribution of the monomer units of the copolymers followed a first‐order Markov statistical model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1800–1807, 2003 相似文献
944.
The aromatic‐aliphatic copolyamides were synthesized by condensation polymerization of aromatic diamine PPD (or APS, where PPD is p‐phenylene diamine and APS is aminophenyl sulfone), aliphatic diamine HDA (or EDA, where HDA is hexanediamine and EDA is ethylenediamine), and TPC (where TPC is terephthalyl chloride) with different molar ratios of aromatic diamine to aliphatic diamine. The steady‐state fluorescence of these condensed copolymers was investigated. These copolyamides exhibit strong blue‐to‐green fluorescence. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 315–321, 2005 相似文献
945.
A new anionic conjugated polymer containing a fluorene group in the main chain was designed and synthesized from poly(2,7‐(9,9′‐dihexylfluorene)‐5,5′‐bibenzimidazole) (PFBI). The polymer showed strong blue emission with high quantum efficiency (0.64) at 450 nm in MeOH and the dramatic quenching effect by Methyl Viologen (MV2+). The fluorescence‐quenching effect results from the weak complex formation between an anionic polymer and electron acceptors such as bipyridinium derivatives. The linear Stern–Volmer constant (Ksv) was 3.7×105 M?1 for MV2+. The newly synthesized polymer is expected to show the applicability for biological and chemical sensors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 900–904, 2004 相似文献
946.
Polyfuran (PFu), poly(2‐bromoaniline) (P2BrAn), and poly(2‐bromoaniline)/polyfuran (P2BrAn/PFu) composites were synthesized by coupling using various solvents and oxidants. 2‐Bromoaniline (2BrAn) was polymerized using FeCl3 and (NH4)2S2O8 in aqueous HCl medium. PFu was synthesized using FeCl3 and SbCl3 in anhydrous media (CHCl3, CH3CN). Furan was polymerized using both salts in CHCl3 medium, whereas it could be polymerized using only FeCl3 in CH3CN medium. The new electrically conducting composites were prepared by chemical oxidative polymerization using polyfuran synthesized with SbCl3 and poly(2‐bromoaniline). The polymers and composites were characterized using conductivity, magnetic susceptibility, infrared spectra (FTIR), UV‐Vis spectra, thermal analysis (TGA), and scanning electron microscopy (SEM) measurements. It was found that PFu(SbCl3) has the lowest thermal stability. Thus, the thermal stability of PFu was increased by preparing composites. The chemical structures of P2BrAns and composites have been found from UV‐Vis results to contain quinone‐imine units along the polymer chain. Magnetic susceptibility measurements indicated that the polymers and composites were diamagnetic or paramagnetic. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2048–2057, 2005 相似文献
947.
增产柴油的有效途径--减一线直接生产柴油 总被引：1，自引：0，他引：1
介绍了一种增产柴油的有效途径———减一线直接生产柴油,即在减一线下增设一个分馏段。与减一线生产催化原料相比,其收率、操作条件、产品性质等只是减一线、减二线有所差别。工程设计的结果是换热网络、机泵、管线、仪表等都相同,增加的工程量及投资较少,经济效益十分显著。 相似文献
948.
Robert D. Van De Grampel Jan Van Geldrop Jozua Laven Rob Van Der Linde 《应用聚合物科学杂志》2001,79(1):159-165
This study aimed at reducing the surface energy of coatings by copolymerization of commonly used monomers with fluorine‐containing monomers. Copolymers of 1,1‐dihydroperfluoroheptyl methacrylate (FHMA) and methyl methacrylate (MMA) or butyl acrylate (BA) are prepared by low‐conversion polymerization in solution. Using 1H‐NMR data and nonlinear least‐squares data fitting, reactivity ratios of these systems at 80°C are determined to be rFHMA = 1.31, rMMA = 0.76, and rFHMA = 3.15, rBA = 0.38, respectively. We assume that the penultimate unit effect plays an important role in these systems. Introduction of the perfluoroalkyl side chain lowers the polymer surface energy significantly; copolymers of MMA and FHMA show a reduction in total surface energy of about 50 % at a content of 15 mol % FHMA as compared with pure PMMA. The attainable reduction in surface energy is much larger than with, for example, Teflon. This is due to the preferential adsorption of the —CF3 groups of the fluoroalkyl side chain, if compared to that of the —CF2— groups of Teflon. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 159–165, 2001 相似文献
949.
A hyperbranched polyol with long flexible chains on the molecule surface was synthesized and characterized. The effect of the hyperbranched polyol as flexibilizer and chain‐transfer agent on cationic UV curing was investigated. It was found the hyperbranched polyol could markedly improve the mechanical properties of cured film. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1353–1356, 2000 相似文献
950.
Poly(2‐chloroaniline) (P2ClAn)/pumice (Pmc) and poly(o‐toluidine) (POT)/Pmc composites were synthesized via the chemical oxidative polymerization of 2‐chloroaniline and o‐toluidine in the presence of a dispersion of Pmc powders in water solvent with an (NH4)2S2O8 oxidant. The composites were characterized with Fourier transform infrared (FTIR) spectroscopy, thermo‐gravimetric/differential thermal analysis (TG‐DTA), and scanning electron microscopy devices. The presence of P2ClAn and POT in the structure of the composites was confirmed by FTIR. Theresults of analysis show strong interactions between the homopolymers and Pmc. The applicability of the P2ClAn/Pmc and POT/Pmc composites were investigated for the removal of Cr(VI) ions in water. Batch adsorption experiments were carried out as a function of pH, initial concentration, time, adsorbent dosage, and temperature. The batch sorption kinetics were tested, and the applicability of the Langmuir and Freundlich adsorption isotherms for this system was tested at 20 ± 1°C. An initial pH of 3.0 was most favorable for Cr(VI) removal by all adsorbents. The adsorption capacities obtained were 0.187 and 4.959 mmol/g of adsorbent for POT/Pmc and P2ClAn/Pmc from the Freundlich and Langmuir adsorption isotherms, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献