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N. I. Boiko I. D. Leshchiner E. V. Agina R. Richardson V. P. Shibaev 《Polymer Science Series A》2011,53(8):645-654
A comparative analysis of the structure and phase behavior of synthesized carbosilane amphiphilic LC dendrimers of the third
generation containing mesogenic phenyl and oligo(ethylene glycol) fragments is performed. When phenol groups are replaced
with oligo(ethylene glycol) moieties, the temperature interval of the existence of the LC phase in the mesogen-containing
dendrimers decreases. The chemical nature of hydrophilic terminal groups is found to control the organization of dendrimers
in the smectic mesophase. Structural models for their packing are proposed. Amphiphilic dendrimers are shown to form stable
Langmuir films at the water/air interface. Surface-pressure-surface area-isotherms are constructed. The effect of the chemical
nature of hydrophilic groups on the formation of a monolayer at the interface and on the packing density of dendrimer molecules
in the monolayer is discussed. 相似文献
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3.
Domenici V Cifelli M Veracini CA Boiko NI Agina EV Shibaev VP 《The journal of physical chemistry. B》2008,112(47):14718-14728
A complete Deuterium NMR study performed on partially deuterated liquid crystalline carbosilane dendrimer is here reported. The dendrimer under investigation shows a SmA phase in a large temperature range from 381 to 293 K, and its mesophasic properties have been previously determined. However, in this work the occurrence of a biphasic region between the isotropic and SmA phases has been put in evidence. The orientational order of the dendrimer, labeled on its lateral mesogenic units, is here evaluated in the whole temperature range by means of (2)H NMR, revealing a peculiar trend at low temperatures (T < 326 K). This aspect has been further investigated by a detailed analysis of the (2)H NMR spectral features, such as the quadrupolar splitting, the line shape, and the line-width, as a function of temperature. In the context of a detailed NMR analysis, relaxation times (T(1) and T(2)) have also been measured, pointing out a slowing down of the dynamics by decreasing the temperature, which determines from one side the spectral changes observed in the NMR spectra, on the other the observation of a minimum in the T(1). 相似文献
4.
E. V. Agina N. I. Boiko R. M. Richardson B. I. Ostrovskii V. P. Shibaev E. A. Rebrov A. M. Muzafarov 《Polymer Science Series A》2007,49(4):412-424
Two series of carbosilane LC dendrimers with terminal protonated and deuterated butoxyphenylbenzoate mesogenic groups linked to carbosilane dendritic matrices of the first to fifth generations via an undecylene spacer have been synthesized. The chemical structure of new dendrimers has been studied by 1H NMR spectroscopy and gel-permeation chromatography. The dendrimers of first-fourth generations are characterized by formation of the smectic C mesophase in a wide temperature range, whereas much more complex columnar supramolecular structures are formed in dendrimers of the fifth generation. Structural studied of mesophases by X-ray diffraction and small-angle neutron scattering show that segregation takes place in mixtures of deuterated and protonated LC dendrimers; as a result, huge aggregates composed of hundreds of chemically unbound molecules develop and the sizes of these aggregates reversibly change with temperature. 相似文献
5.
Leshchiner I Agina E Boiko N Richardson RM Edler KJ Shibaev VP 《Langmuir : the ACS journal of surfaces and colloids》2008,24(19):11082-11088
The first series of carbosilane liquid crystal codendrimers with groups of different polarity has been synthesized. The chemical structure of the newly synthesized materials and the composition of the codendrimers were studied by NMR spectroscopy and MALDI-TOF MS. It was found that the codendrimers tend to form stable Langmuir films at the air-water surface. The influence of composition and generation number on surface pressure-surface area isotherms and film stability was studied. Brewster angle microscopy confirmed the different phase behavior for monolayers of different codendrimer composition and generation number. It was found that side groups of fifth-generation codendrimers do not segregate, unlike those of lower generations. Langmuir-Blodgett films on solid substrates were obtained by the vertical dipping method. X-ray diffraction showed that the codendrimers with 75% of hydrophobic mesogenic terminal groups formed ordered layers parallel to the substrate. 相似文献
6.
Komolov A. S. Lazneva E. F. Zhukov Yu. M. Pshenichnyuk S. A. Agina E. V. Dominskii D. I. Anisimov D. S. Parashchuk D. Yu. 《Physics of the Solid State》2017,59(12):2491-2496
Physics of the Solid State - Atomic composition of monolayers based on siloxane dimer of quaterthiophene deposited by Langmuir–Blodgett technique on a silicon dioxide surface partially... 相似文献
7.
Subham Majumdar EV Sampathkumaran St Berger M Della Mea H Michor E Bauer M Brando J Hemberger A Loidl 《Pramana》2002,58(5-6):777-782
Recently, the solid solution Ce2Au1−
x
Co
xSi3 has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo
effect. Here we report high pressure electrical resistivity of Ce2AuSi3, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these
alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which
are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions
before attaining non-magnetism for the Co end member. 相似文献
8.
I. D. Leshchiner E. V. Agina N. I. Boiko R. Richardson V. P. Shibaev 《Russian Chemical Bulletin》2008,57(10):2101-2110
Amphiphilic carbosilane liquid-crystalline codendrimers with terminal mesogenic butoxybenzoate and phenolic groups have been synthesized for the first time. The structures and compositions of the synthesized codendrimers were characterized by NMR spectroscopy. The data from polarization optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering demonstrated that all codendrimers possessed mesomorphic properties. They form thin (Langmuir) films at the water-air interface. The surface pressure-surface area isotherms were plotted. The Langmuir-Blodgett films of different thicknesses were obtained by the vertical dipping method on the solid substrate. The film structures were studied by grazing incidence X-ray diffraction analysis. 相似文献
9.
We have grown single crystals of the psuedo-one-dimensional compound Sr3CuIrO6, a K4CdCl6-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior
of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence
for at least two magnetic transitions, at 5 K (T
1) and 19 K (T
2), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of
both the forms is found to be widely different, exhibiting unexpected time dependence. 相似文献
10.
General concepts of organic (polymeric) electronics are given, a relationship between chemical structure of semiconducting
macromolecular systems and their electronic properties is considered, main approaches to the control of these properties are
listed. A relationship between dimensionality of the systems considered (one-, two-, and three-dimensional) and a possibility
to control their molecular organization, as well as their practical use are illustrated. Typical representatives of both the
linear and branched (two- and three-dimensional) macromolecules, approaches to the synthesis of such macromolecules, their
optical and electrical properties, as well as prospective fields of application, are considered. 相似文献
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