共查询到20条相似文献,搜索用时 109 毫秒
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双官能团引发剂进行的基团转移嵌段共聚 总被引:1,自引:2,他引:1
嵌段共聚物的合成技术有较大的可靠性和预见性,并可提供别的聚合物所不能达到的特殊性能。用基团转移聚合的方法进行丙烯酸酯类极性单体室温下的活性聚合,能得到具有预定链长、嵌段纯度和多分散性指数小的嵌段共聚物。用双官能团引发剂进行基团转移嵌段共聚,可减少加单体的次数,避免引进杂质,且能合成用单官能团引发剂所无法得到的A—B— 相似文献
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大分子引发剂用于合成嵌段液晶共聚物的新进展 总被引:1,自引:0,他引:1
前有多种制备嵌段液晶共聚物的方法,采用大分子引发剂合成嵌段液晶共聚物,方法简单且易于实施,越来越受到人们的青睐。综述了由大分子引发剂合成嵌段液晶共聚物方面取得的新进展。 相似文献
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一、前言大分子引发剂(macroinitiator)是指在分子链上带有可分解成自由基的偶氮、过氧基的高分子化合物。早在五十年代,Shah就报道过这种高分子化合物的合成,他用邻苯二甲酰氯与过氧化钠反应制成聚邻苯二甲酸过氧化 相似文献
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用大分子引发剂法制备嵌段共聚物 总被引:6,自引:0,他引:6
主要介绍了用大分子引发剂法制备嵌段共聚物的方法。大分子引发剂是从已商品化的功能聚合物制得或用其它活性聚合方法合成。从单封端的端羟基聚合物、其它单官能团或双官能团聚合物以及双功能基团缩聚物制得大分子引发剂.然后用于原子转移自由基聚合(ATRP)、氮氧稳定自由基聚合以及可逆加成裂解链转移(RAFT)聚合等.可制得结构可控、分子量分布窄的嵌段共聚物。 相似文献
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活性阳离子聚合法合成嵌段共聚物的研究进展 总被引:2,自引:0,他引:2
在80年代,阳离子聚合研究的一个最重要突破可能就是活性阳离子聚合。目前为止,有关活性阳离子聚合的新引发体系,新单体及合成应用等方面已取得巨大进展,本综述主要介绍利用活性阳离子聚合合成二、三元嵌段和多元嵌段共聚物的研究成果。 相似文献
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O. V. Khilya O. V. Shablykina M. S. Frasinyuk V. V. Ishchenko V. P. Khilya 《Chemistry of Natural Compounds》2005,41(5):523-528
3-(2-Pyridyl)coumarins were prepared by reaction of substituted salicylaldehydes and 2-pyridylacetonitrile. Benzylation, acylation,
and aminomethylation of 7-hydroxy-3-(2-pyridyl)coumarin was studied.
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Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 428–431, September–October, 2005. 相似文献
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Khenglawt Pachhunga Bruno Therrien Kevin A. Kreisel Glenn P.A. Yap Mohan Rao Kollipara 《Polyhedron》2007
The reaction of [CpRu(PPh3)2Cl] and [CpOs(PPh3)2Br] with chelating 2-(2′-pyridyl)imidazole (N ∩ N) ligands and NH4PF6 yields cationic complexes of the type [CpM(N ∩ N)(PPh3)]+ (1: M = Ru, N ∩ N = 2-(2′-pyridyl)imidazole; 2: M = Ru, N ∩ N = 2-(2′-pyridyl)benzimidazole; 3: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-dimethylimidazole; 4: M = Ru, N ∩ N = 2-(2′-pyridyl)-4,5-diphenylimidazole; 5: M = Os, N ∩ N = 2-(2′-pyridyl)imidazole; 6: M = Os, N ∩ N = 2-(2′-pyridyl)benzimidazole). They have been isolated and characterized as their hexafluorophosphate salts. Similarly, in the presence of NH4PF6, [Cp∗Ir(μ-Cl)Cl]2 reacts in dry methanol with N ∩ N chelating ligands to afford in excellent yield [Cp∗Ir(N ∩ N)Cl]PF6 (7: N ∩ N = 2-(2′-pyridyl)imidazole; 8: N ∩ N = 2-(2′-pyridyl)benzimidazole). All the compounds have been characterized by infrared and NMR spectroscopy and the molecular structure of [1]PF6, [2]PF6 and [7]PF6 by single-crystal X-ray structure analysis. 相似文献
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Pradipta PurkayasthaNitin Chattopadhyay 《Journal of Molecular Structure》2002,604(1):87-99
Semi-empirical (AM1-SCI) calculations have been performed on 2-(2′-hydroxyphenyl)oxazole (HPO), 2-(2′-hydroxyphenyl)imidazole (HPI) and 2-(2′-hydroxyphenyl)thiazole (HPT) to rationalise the photophysical behaviour of the compounds exhibiting intramolecular rotation as well as excited state intramolecular proton transfer (ESIPT). The calculations reveal that there is a gradual variation in the properties from HPO to HPT through HPI so far as the existence of the rotational isomers in the ground state is concerned. While HPO gives rise to two stable rotamers (I and II) in all the common solvents, there is only one stable species for HPT in the S0 state. For HPI, rotamer II is possible only in the isolated state and/or in solvents of low polarity, but in high polar solvents it gives rise to the normal form (I) only. For all the molecules in the series, however, intramolecular proton transfer (IPT) takes place in the lowest excited singlet (S1) and the triplet (T1) states. Combination of the rotamerism and ESIPT gives rise to multiple fluorescence bands for the fluorophores. Theoretical assignments have been made for the excitation, fluorescence and phosphorescence bands. Simulated potential energy curves (PEC) in different electronic states reveal that the IPT process is feasible in either of the S1 and T1 states but not in the ground state. The ESIPT reaction has been found to be favoured both thermodynamically and kinetically in these electronic states compared to the ground state. However, quantum mechanical tunnelling has been proposed for the prototropic reaction to proceed in the excited states. 相似文献
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《Arabian Journal of Chemistry》2020,13(6):5900-5910
The pH detection in the alkaline range is particularly important in many fields such as leather processing, waste water treatment, paper industry, and metal mining and finishing. Compared with traditional analysis methods such as colorimetric sensors and electrochemical sensors, the fluorescence and colorimetric probes for pH measurements have attracted much more attention due to their advantages of high sensitivity, excellent selectivity, noninvasiveness, low cost, fast response time, the possibility of continuously measurement, etc. However, there are few fluorescent probes fiting for alkaline pH monitoring. Acturally, the design and synthesis of them were more significant for new probes producing. In this study, the design, synthesis, and practical application of two novel fluorescent pH probes for alkaline pH assay were discussed. Both of the two probes were derived from perylene tetra-(alkoxycarbonyl). The red or blue shift of the absorption/fluorescence spectrum was caused by the introduction of electron donor amino or oxygen ring in the bay region. Due to electronic separation of the OH group from the electron-withdrawing core, the probes have high pKa values and cover the pH range from 8 to 12. They exist in either fluorescent acid form or non-fluorescent basic form. It was investigated that the amino substituent at bay region had a higher pKa value than O-heterocyclic annulated perylene, which showed that the adjustable pKa value could be achieved by the modification of electron withdrawing groups. The probes would have a wide use for testing strips measurements and monitoring pH changes in concrete. 相似文献
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2-(2-Furyl)-1-methyl-1H-acenaphtho[9,10-d]imidazole was obtained by the condensation of 9,1-acenaphthenequinone with furfural
in the presence of ammonium acetate followed by N-methylation of the obtained 2-(2-furyl)-1H-acenaphtho[9,10-d]imidazole with
methyl iodide in N-methylpyrrolid-2-one in the presence of potassium hydroxide. It was established that its electrophilic
substitution in an acidic medium only takes place at position 2 of the furan ring while in a neutral medium both position
2 and position 7 of the aromatic part of the molecule undergo electrophilic attack.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 191–196, February, 2006. 相似文献
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《Journal of Coordination Chemistry》2012,65(10):1107-1121
Four copper(II) supramolecular complexes, {[Cu(Hpb)(mal)]·H2O} n (1), (Hpb?=?2-(2-pyridyl)-benzimidazole, mal?=?maleate), [Cu4(pb)4(cro)4(MeOH)2]·2MeOH (2) (cro?=?crotonate), [Cu2(pb)(Hpb)(mac)3(MeOH)] (3) (mac?=?α-methacrylate) and [Cu(Hpb)(acr)2(H2O)] (4) (acr?=?acrylate), based on carboxylate copper(II)-aromatic ligand systems which are assembled by combination of metal coordination, hydrogen-bond and π–π interactions, have been rationally designed and synthesized. Complex 1 forms a 3D supramolecular network with open channels by extending 2D undulating sheets constructed from 1D helical chains. Complex 2 generates a 2D grid-like sheet via unusual finite-chain tetranuclear molecules, with four copper atoms arranged in a line; the unit does not extend further due to the capping effect of the terminal methanol. Complexes 3 and 4 present a 1D sinusoidal structure and a 3D columnar network with 1D ladder-shaped double chains, respectively. Interestingly, coligand Hpb, deprotonated or/and neutral in different supramolecular complexes, provides hydrogen bonding and π–π stacking interactions. In complexes 2, 3 and 4, carboxylate anions show various bridging modes, which are reflected in their magnetic properties. Weak ferromagnetic coupling (syn-anti µ-OCO) exists in 1, antiferromagnetic (syn-syn µ-OCO) and weak ferromagnetic coupling (µ-O of the??COO group) in 2 and antiferromagnetic coupling (syn-syn µ-OCO) in 3. 相似文献
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研究了稀土元素La3+、Gd3+、Yb3+、Lu3+、Y3+及Sc3+对Eu-2-(2-二苯乙酰基)-1,3-茚二酮-阳离子表面活性剂体系的荧光增强效应,结果表明,在上述增强离子存在下,体系的荧光强度分别增加10、130、30、50、52和20倍,利用标准加入法测定了混合稀土氧化物中的铕,铕浓度在1.0×10-10~6.0×10-7mol/L范围内与荧光强度呈线性关系,最低检出限为6.0×10-12mol/L. 相似文献