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T. K. Kwei Kalle Levon Giuliana Tesoro Frank Liu Abraham Mey-Marom Surya Munukutla 《先进技术聚合物》1993,4(9):537-547
The synthesis of molecular composites where rigid polymer molecules are reinforcing elements in a thermoset bisimide matrix has been investigated. The approach has been designed to avoid phase separation by selecting systems where reaction of amine-terminated rigid and semiflexible oligomers with maleimide unsaturation occurs prior to crosslinking of the thermoset. This objective has been met for some compositions. The concentration and molecular weight of the rigid oligomers have been varied. The structure of the reinforcing polymer, the reactivity of the maleimide and the conditions for composite synthesis are variables of critical importance, and further work must determine the promise and limitations of this approach. 相似文献
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Sergey A. Nazarov Andrey S. Slutskij Jari Taskinen 《Mathematical Methods in the Applied Sciences》2014,37(16):2463-2483
We consider an elastic rod with rounded ends and diameter proportional to a small parameter h > 0. The roundness of the ends is described by an exponent m ∈ (0,1). We derive for the rod an asymptotically sharp Korn inequality with a special weighted anisotropic norm. Weight factors with m‐dependent powers of h appear both in the anisotropic norm and the Korn inequality itself, and we discover three critical values m = 1 ∕ 4, m = 1 ∕ 2 and m = 3 ∕ 4 at which these exponents are crucially changed. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Successive stepwise evolution of host layer‐stacking framework upon the intercalation of mobile vapor guests within side‐chain layers
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Bei‐Kai Yang Chen‐An Wang Wen‐Yan Zhang Jrjeng Ruan 《Journal of Polymer Science.Polymer Physics》2017,55(19):1448-1457
For the ordered phases of hairy‐rod semiconductive poly(2,5‐bis(3‐tetradecylthiophene‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) sandwiched in between crystalline platelets of hexamethylbenzene, the successive stepwise evolution of layer‐stacking framework upon guest intercalation has been studied in this research. The direct consequence of the guest intercalation into side‐chain layers is evaluated to cause the lateral shift of thiophene backbones along π–π stacking, resulting in stepwise shift of ultraviolet absorption wavelength. The thermal motions of vapor guests within disordering side‐chain layers subsequently cause progressive expansion of host stacking framework. With the increase in side‐chain length, thicker layers of disordering side chains in liquid crystals (LCs) accommodate additional vapor guests and larger amplitudes of thermal motions of guests, hence promoting the level of reversible d‐spacing change. The mixing between mobile vapor guests and aliphatic side chains is clarified as the mechanism of guest intercalation, which rationalizes successive guest intercalation during heating and the contribution of disordering side‐chain layers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1448–1456 相似文献
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Monosaccharides and disaccharides are important dietary components, but if insufficiently metabolized by some population subgroups, they are also linked to disease patterns. Thus, the correct analytical identification, quantification, and labeling of these food components are crucial to inform and potentially protect consumers. Enzymatic assays and high-performance anion-exchange chromatography with pulsed amperometric detection are established methods for the quantification of monosaccharides and disaccharides that, however, require long measuring times (60–180 min). Accelerated methods for the identification and quantification of the nutritionally relevant monosaccharides and disaccharides d -glucose, d -galactose, d -fructose, sucrose, lactose, and maltose were therefore developed. To realize this goal, the NMR experiments HSQC (heteronuclear single quantum coherence) and acceleration by sharing adjacent polarization (ASAP)-HSQC were applied. Measurement times were reduced to 27 and 6 min, respectively, by optimizing the interscan delay and applying non-uniform sampling. The optimized methods were used to quantify d -glucose, d -galactose, d -fructose, sucrose, and lactose in various dairy products. Results of the HSQC and ASAP-HSQC methods are equivalent to the results of the reference methods in terms of both precision and accuracy, demonstrating that these methods can be used to correctly analyze nutritionally relevant monosaccharides and disaccharides in short times. 相似文献
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Pascal Rusch Denis Pluta Dr. Franziska Lübkemann Dr. Dirk Dorfs Dr. Dániel Zámbó Prof. Nadja C. Bigall 《Chemphyschem》2022,23(2):e202100755
Employing nanocrystals (NCs) as building blocks of porous aerogel network structures allows the conversion of NC materials into macroscopic solid structures while conserving their unique nanoscopic properties. Understanding the interplay of the network formation and its influence on these properties like size-dependent emission is a key to apply techniques for the fabrication of novel nanocrystal aerogels. In this work, CdSe/CdS dot/rod NCs possessing two different CdSe core sizes were synthesized and converted into porous aerogel network structures. Temperature-dependent steady-state and time-resolved photoluminescence measurements were performed to expand the understanding of the optical and electronic properties of these network structures generated from these two different building blocks and correlate their optical with the structural properties. These investigations reveal the influence of network formation and aerogel production on the network-forming nanocrystals. Based on the two investigated NC building blocks and their aerogel networks, mixed network structures with various ratios of the two building blocks were produced and likewise optically characterized. Since the different building blocks show diverse optical response, this technique presents a straightforward way to color-tune the resulting networks simply by choosing the building block ratio in connection with their quantum yield. 相似文献
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《Current Applied Physics》2015,15(3):356-362
This paper reports a new method for fabricating two-dimensional ZnO nanorod patterns. A water soluble mixture of poly(vinyl alcohol)-N-methyl-4(4′-formylstyryl)pyridinium methosulfate acetal (PVA-Sbq) and zinc acetate (ZnA) was used as a negative photoresist to produce the desired patterns using conventional photolithography. Hydrothermally-grown ZnO nanorods were grown selectively on the calcined PVA-Sbq/ZnA patterns. The appropriate concentration of PVA-Sbq and ZnA that can produce the desirable seed layer pattern was determined experimentally. Furthermore, the effects of the calcination time on the morphology and vertical alignment of ZnO nanorods were investigated. The vertically-aligned ZnO nanorods were generated by sufficient calcination of the patterned seed layer. On the other hand, the aspect ratio of ZnO nanorods decreased slightly with increasing calcination time. This new approach provides a simple and cost-effective method for fabricating ZnO nanorod patterns which can be beneficial in various solid-state devices and optoelectronic applications. 相似文献
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