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251.
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Doris Fischer‐Henningsen 《Chemie in Unserer Zeit》2002,36(3):147-147
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Doris Pospiech Liane Hußler Kathrin Eckstein Dieter Jehnichen Antje Gottwald Petra Ptschke 《Macromolecular Symposia》2000,149(1):219-224
One mechanism for compatibilization of immiscible polymer blends is adding block copolymers (BCP) that consist of segments chemically comparable to the parent homopolymers in the blend. BCP do both, emulsify the disperse phase to give smaller particles as well as increase the interfacial adhesion between the phases. The influence of segmented BCP in blends of immiscible high‐performance polymers was investigated systematically by variation of the flexibility of the BCP segments. It was shown that the stiffness of the second segment in polysulfone (PSU) block copolymers as well as the PSU segment molecular weight determine the intermixing between the BCP and the PSU matrix. 相似文献
254.
Doris Pfeiffer Rolf-Günter Kretschmer Siegfried Hoffmann 《Crystal Research and Technology》1986,21(10):1321-1325
The compound 1-[4-n-heptylbenzoyl]-2-[cyanoacetyl]-hydrazine crystallizes in the triclinic space group Pl̄ with two molecules in the unit cell and the lattice parameters a = 4.702, b = 8.640, c = 20.906 Å, a = 97.50, β = 92.79, γ = 100.19°. The structure was solved by direct methods and refined by full-matrix least squares calculations to the final residual value R = 0.039. 相似文献
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Rafael J. Rasse Rosa M. Domínguez Armando Herize Maria Tosta Doris Brusco Gabriel Chuchani 《Journal of Physical Organic Chemistry》2007,20(1):44-48
A homogeneous, molecular, gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐ buten‐3‐ol catalyzed by hydrogen chloride in the temperature range 325–386 °C and pressure range 34–149 torr are described. The rate coefficients are given by the following Arrhenius equations: for 2‐phenyl‐2‐propanol log k1 (s?1) = (11.01 ± 0.31) ? (109.5 ± 2.8) kJ mol?1 (2.303 RT)?1 and for 3‐methyl‐1‐buten‐3‐ol log k1 (s?1) = (11.50 ± 0.18) ? (116.5 ± 1.4) kJ mol?1 (2.303 RT)?1. Electron delocalization of the CH2?CH and C6H5 appears to be an important effect in the rate enhancement of acid catalyzed tertiary alcohols in the gas phase. A concerted six‐member cyclic transition state type of mechanism appears to be, as described before, a rational interpretation for the dehydration process of these substrates. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
258.
Vollmer D Hinze G Ullrich B Poon WC Cates ME Schofield AB 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):4921-4930
In mixtures of thermotropic liquid crystals with spherical poly (methyl methacrylate) particles, self-supporting networklike structures are formed during slow cooling past the isotropic-to-nematic phase transformation. To characterize the process of network formation in terms of morphology, phase transformation kinetics, and mechanical properties, we have combined data from polarization and laser scanning confocal microscopy with calorimetric, NMR, and rheological results. Our data suggest that the mechanism of network formation is dominated by a broadened temperature and time interval of phase transformation rather than by particle size or concentration. The observation that the width of the transformation interval strongly depends on sample preparation supports the hypothesis that a third component, most likely alkane remnants slowly liberated from the particles, plays a crucial role. In addition, calorimetric findings for liquid crystal/colloid mixtures, heated and cooled up to 13 times, point to separation of the liquid crystal into two compartments with different phase transformation kinetics. This could be explained by redistribution and enrichment of alkane in the particle-composed network walls. A further increase of the storage modulus, G', and incomplete dissolution of the networks in the isotropic state indicate that the formation of two compartments during repeated temperature cycles stabilizes the network and confers strong memory effects. 相似文献
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