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911.
A novel Schiff base type polyester containing 2,2’-diamino-4,4’-bithiazole(DABT) was prepared by low-temperature interface polycondensation of 1,4-benzenedicarbonyl dichloride with 4,4’-(4,4’-bithiazole-2,2’-diylbis(imine-2,1-diyl)diphenol(BDDP), which is derived from a 2,2’-diamino-4,4’-bithiazole(DABT) Schiff base reacted with a 4-hydroxybenzaldehyde monomer.The newly generated polyester was evaluated based on characterization of its solubility,FTIR spectroscopy,elemental analysis,X-ray diffraction measurements and thermogravimetric analysis(TGA) studies. 相似文献
912.
A protocol for the copper-catalyzed C-S bond formation between aryl, alkyl, or heteroaryl thiols and aryl or heteroaryl halides is reported. The reaction is catalyzed by Cu2O which shows the highest catalytic activity with ethyl 2-oxocyclohexanecarboxylate ligand in DMSO at 80 °C. The corresponding coupling products are obtained with good to excellent yields under relatively mild reaction conditions with good chemoselectivity and functional group tolerance. 相似文献
913.
陷阱型双通带声表面波滤波器的设计 总被引:1,自引:1,他引:0
研究比较了几种陷阱型双通带声表面波滤波器的设计方法。实验表明,采用组合式均匀叉指换能器及变形多条耦合器元件可有效提高对陷阱频率的抑制。 相似文献
914.
Cong Deng Yan Yang Meng Gao Yan-Ping Zhu An-Xin Wu Jun-Rui Ma Guo-Dong Yin 《Tetrahedron》2012,68(20):3828-3834
2-Methylthio-substituted 1,4-enediones, obtained from readily available aryl methyl ketones, were reacted with primary or secondary amines to afford the desired 1,4-diaryl-2-aminobut-2-ene-1,4-diones in excellent yields with high Z/E-stereoselectivity. 相似文献
915.
916.
Special crystallization event of isotactic polypropylene (iPP) in a constrained environment, a layered clay network, was followed by in situ Fourier transform infrared (FTIR) spectroscopy during the cooling process. Before occurrence of nucleation/crystallization, a conformationally ordered phase, which consists of significant amounts of long 31 helices with 14 monomeric units, has been identified for the first time. More importantly, it was found that the long‐ordering helices could play a more important role than short ones for the confined crystallization. It could be tentatively explained as due to the existence of constrained regions in the proximity of the nanoclay platelets or tactoids and the heterogeneous nucleation capability of the surface of nanoclay. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
917.
Xiaofeng Luo Xiaoqing Liu Bo Chen Jianping Deng Wantai Yang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5611-5617
A facile methodology was developed to prepare a novel type of core/shell nanoparticles (NPs) with optical activity and with chemical bonds between the cores and shells. The cores were prepared via catalytic emulsion copolymerization of substituted acetylene comonomers in which one monomer contains azo groups in side chains. For preparing the core/shell NPs, the azo groups in the seed particles (i.e., cores) subsequently act as initiators for vinyl monomer to undergo free radical polymerizations, yielding the shells. This situation resulted in chemical bonds between cores and shells. Both the seed emulsion and core/shell nanoparticle emulsion exhibited optical activity, derived from the polyacetylenes adopting helical conformation of predominant handedness. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
918.
919.
DABCO-catalyzed dimerization of Morita–Baylis–Hillman acetates to synthesize a series of 3-alkyl-4-(E)-alkenyl-cyclohex-1-ene-1,4-dicarbonyl compounds in excellent yields with modest to excellent diastereoselectivity is reported. A plausible reaction mechanism is also proposed on the basis of previous literature and preliminary investigation the asymmetric version of the reaction. 相似文献
920.
Xueqing Qiu Xiongyi Peng Yonghong Deng 《Journal of Dispersion Science and Technology》2013,34(2):203-212
Polycarboxylate-type superplasticizers (PCs) containing different side chains and sulfonic groups have been synthesized, and the effect of side chains and sulfonic groups on their performance in cementitious systems has been intensively investigated by measuring zeta potential, thickness of absorption layer, paste fluidity, rheological properties as well as the setting time in this paper. Results show that the PC containing both short poly(ethylene oxide) (PEO) side chains and long PEO side chains with the molar ratio of 1:1 has a better dispersibility than the PC containing only short PEO side chains or only long PEO side chains in cement suspensions. The shorter the side chain of the PC, the longer the setting time of cement paste incorporating it. An appropriate increase of sulfonic group content is beneficial for the improvement of dispersibility for the PC and leads to no obvious change for the setting time. It also suggests that there is a geometrical balance between the PEO side chains and sulfonic groups for the performance of PC. This work is not only helpful for understanding the relationship of molecular structure of PCs and their performance, but also further designing optimum molecular structure of PC to meet the requirement in different concrete system. 相似文献