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Sergei V. Kostjuk Hui Yee Yeong Brigitte Voit 《Journal of polymer science. Part A, Polymer chemistry》2013,51(3):471-486
This review highlights recent approaches toward polyisobutylene (PIB) by an energy efficient room temperature cationic polymerization. Special focus is laid on our own work using modified Lewis acids and nitrile‐ligated metal complexes associated with weakly coordinating anions. In both cases, suitable conditions have been found for efficient production of PIB characterized by medium to low molar masses and a high content of exo double bonds as end groups—the typical features of highly reactive PIB, an important commercial intermediate toward oil and gasoline additives. These and other approaches demonstrate that the cationic polymerization of isobutylene is still not fully explored, and new innovative catalyst systems can lead to surprising results of high commercial interest. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
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Treatment of pyridine borane (Py.BH3) with iodine, bromine, or strong acids affords activated Py.BH2X complexes that are capable of hydroborating alkenes at room temperature. Evidence is presented for an unusual hydroboration mechanism involving leaving group displacement. In contrast to THF.BH3, hydroboration with Py.BH2I selectively affords the monoadducts. The crude hydroboration products are converted into synthetically useful potassium alkyltrifluoroborate salts upon treatment with methanolic KHF2. 相似文献
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GONG YongYang TAN YeQiang LI Hong ZHANG YiRen YUAN WangZhang ZHANG YongMing SUN JingZhi TANG Ben Zhong 《中国科学:化学(英文版)》2013,56(9):1183-1186
Efficient room temperature phosphorescence (RTP) is rarely observed in pure organic luminogens. However, we have newly observed that benzil and its derivatives are nonluminescent in solvents and thin layer chromatography (TLC) plates, but become highly phosphorescent in crystal state at room temperature, exhibiting typical crystallization-induced phosphorescence (CIP) characteristics. The CIP phenomenon is ascribed to the restriction of intramolecular rotations in crystals owing to effective intermolecular interactions. Such intermolecular interactions greatly rigidify the molecular conformation and significantly decrease the nonradiative deactivation channels of the triplet excitons, thus giving boosted phosphorescent emission at room temperature. 相似文献
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Through Differential Scanning Calorimetry (DSC), at least three room temperature transitions are clearly observable for native polytetrafluoroethylene (PTFE). The influence of the thermal history on the room temperature transitions has been investigated. Possible interpretations for the lowest room temperature transition are suggested.
Dr. G. Ajroldi and Prof. G. Guerra are gratefully acknowledged for useful advice and stimulating discussions. 相似文献
Zusammenfassung Bei der Untersuchung von nativen Polytetrafluoroethylen (PTFE) lassen sich im Raumtemperaturbereich zumindest drei Umwandlungen eindeutig beobachten. Der Einfluss der termischen Vorgeschichte von PTFE Proben auf die Umwandlungen im Raumtemperaturbereich wurde untersucht.Mögliche ErklÄrungen für den tiefstliegenden übergang im genannten Temperaturbereich werden vorgeschlagen.
Dr. G. Ajroldi and Prof. G. Guerra are gratefully acknowledged for useful advice and stimulating discussions. 相似文献
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Valtchev VP Tosheva L Bozhilov KN 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10724-10729
Zeolite A nanoparticles were synthesized under room-temperature conditions from a very reactive organic-template-free gel system. The optimization of the syntheses parameters, namely, the composition of the initial system and the careful choice of the reactants, allowed the crystallization to be accomplished within 3 days. At this stage the individual zeolite crystals were in the range of 100-300 nm without well-developed crystal faces. The prolongation of the synthesis time up to 10 days led to formation of larger well-faceted cubic crystals averaging about 400-500 nm in size. The high-resolution transmission electron microscopy (HRTEM) study revealed that a thin layer of amorphous material covers the zeolite particles acting as a binder between individual zeolite crystals. The postsynthesis treatment of the product in NH(3) media under ultrasonic radiation disintegrated the loosely attached zeolite particles and decreased the fraction of zeolite A particles with low colloidal stability. The employed approach, however, did not result in complete disintegration of aggregated crystals. The zeolite crystals obtained under ambient conditions were characterized by XRD, SEM, dynamic light scattering, and N(2) adsorption measurements. 相似文献
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E. R. Volkova V. V. Tereshatov V. I. Karmanov M. A. Makarova A. I. Slobodinyuk 《Polymer Science Series D》2013,6(2):120-124
The influence of polyfunctional hydroxyl-containing oligomer on the rheological, physicomechanical, and adhesive properties of polyurethane composite based on multicomponent oligomer blend and polyisocyanate is investigated. The kinetics of curing is investigated by the viscometric method, and the composition lifetime is determined. It is shown that the polyurethanes under investigation can be used as fast-curing adhesive composites of cold curing operating in a temperature interval of up to +90°C. 相似文献
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A facile, fluoride-induced transition-metal-free chemoselective α-arylation of β-dicarbonyl compounds (malonamide esters) at room temperature using aryne intermediates has been demonstrated. Selective mono- or diarylation and generation of a quaternary benzylic stereocenter have also been achieved. The methodology will be highly useful for the synthesis of a library of CNS depressant barbiturate drugs like Phenobarbital. 相似文献
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We have probed single-molecule metal-to-ligand charge transfer (MLCT) dynamics of a ruthenium complex at room temperature. Using photon antibunching measurements under continuous wave (CW) laser excitation, nonclassical photon statistics, and excitation power dependent measurements, we were able to selectively measure the single-molecule MLCT state lifetime. This work demonstrated, as the first single-molecule photon antibunching measurement of the triplet excited state, a new application of single-molecule spectroscopy on excited-state dynamics and ground-state recovering dynamics of an important class of chemical species that have often been used and studied in energy conversion and electron transfer. 相似文献
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Radmila Krupkov Jan Fbry Ivana Císaov Pemysl Vank 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(5):i66-i68
The title room‐temperature phase of (NH4)2(PO3F) is orthorhombic (Pna21) and is related to the β‐K2SO4 structure family. The title structure consists of ammonium cations, NH4+, and fluorophosphate anions, (PO3F)2?. These ions are connected by N—H?O hydrogen bonds. Two‐centre N—H?F hydrogen bonds are not present in the structure. Phase transitions were detected at 251±2 and 274±2 K during cooling and heating, respectively. 相似文献
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《Journal of the Less Common Metals》1984,96(1):L1-L3
In the system CsTe the compounds Cs2Te, Cs3Te2, Cs2Te3, Cs2Te5 and CsTe4 are stable at room temperature. The powder pattern of Cs2Te was indexed. 相似文献
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Shancheng Yan Dong Hu Jiansheng Wu Jiqing Qian Yuanyuan Wang Zhongdang Xiao 《Solid State Sciences》2010,12(8):1507-1510
The CdS nanowires synthesized by solvothermal route are rapidly elongated in the presence of the ethylenediamine by ultrosonication method at room temperature. Transmission electron microscopy (TEM) analysis reveals that the influential factors on the rapid elongate process are the concentration of ethylenediamine and duration of the ultrosonication reaction. The elongated CdS nanowires are further characterized by UV–vis absorption spectra, which has no apparent difference in the position of the maximum absorption peak comparing with the starting CdS nanowires synthesized by solvothermal method. A mechanism of oriented attachment is proposed to explain the phenomena based on a series of experimental results. 相似文献
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Xianfeng Du Kai Men Youlong Xu Bing Li Mingqi Gao Zihan Liu Shengchun Mao Wasif ur Rehman 《Journal of Sol-Gel Science and Technology》2014,72(2):310-313
Ultrafine titanium dioxide (TiO2) nanocrystal has attracted enormous interest due to their unusual quantum and surface effects. Here, we propose a facile route to synthesize ultrafine anatase nanocrystal at room temperature via an aqueous sol–gel method using lactic acid (LA) and acetylacetone (Acac) as double chelators. Transmission electron microscopy (TEM) and size analyzer confirmed that TiO2 nanocrystal in precursor possessed an average size of ~3 nm with a narrow size distribution. Crystal structure characterized by TEM and X-ray diffraction (XRD) indicated that TiO2 nanocrystal to be anatase phase. The results of field emission scanning electron microscopy (FE-SEM) and BET surface area exhibited that TiO2 xerogel powder had mono-dispersed particles size and large BET surface area up to 90 m2/g. 相似文献