排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
E. B. Barmatov A. S. Medvedev D. A. Pebalk M. B. Barmatova N. A. Nikonorova S. B. Zezin V. P. Shibaev 《Polymer Science Series A》2006,48(7):665-675
A new approach is proposed for the preparation of a new class of hybrid polymer systems based on comb-shaped LC polymers with cyanobiphenyl mesogenic groups and silver nanoparticles with dimensions ranging from 5 to 54 nm. A correlation between copolymer composition and dimensions of the formed nanoparticles is established. As the concentration of nanoparticles in LC copolymer is increased, the resultant glass transition temperature increases, and the temperature interval of the existence of LC phase is reduced. This behavior is related to the adsorption of cyanobiphenyl and carboxylic polymer groups on the surface of silver nanoparticles. In this case, the conductivity and dielectric permittivity of the composites are also increased. 相似文献
2.
A. N. Yunuskhodzhaev EB. Shamuratov A. S. Batsanov S. A. Talipov 《Chemistry of Natural Compounds》1992,27(6):743-744
A single crystal of (RS)-carnitine hydrochloride has been obtained, and its crystal structure has been refined by an x-ray structural experiment.Tashkent Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 842–844, November–December, 1991. 相似文献
3.
A new approach for the preparation of chiral nematic materials is described. The induction of a chiral nematic phase in hydrogen-bonded blends of smectic comb-shaped LC copolymers containing alkyloxy-4-oxybenzoic acid fragments with a low molar mass chiral dopant (a derivative of pyridine) was observed. 相似文献
4.
Hydrogen-bonded blends based on smectic side group functionalized LC copolymers containing 4-alkyloxybenzoic acid fragments (proton donor) and a non-mesogenic low molecular mass dopant 4-cyanophenyl pyridine-4-carboxylate or 4-methoxyphenyl-d4 pyridine-4-carboxylate (proton acceptor) were obtained. The blends containing 10-35 mol % of low molecular weight dopant form nematic (I-N-SmA) or re-entrant SmA phases (I-SmA-N-SmAre). The temperature dependence of the order parameter S, the birefringence Δn, and the splay K 1 and bend K 3 elastic constants of the nematic phase were studied by 2H NMR spectroscopy and the Fréedericksz method of threshold transitions in a magnetic field. A mechanism for the destruction of the SmA phase and the formation of the nematic phase in the hydrogen-bonded blends is suggested. 相似文献
5.
Trapped modes in acoustic waveguides 总被引:2,自引:0,他引:2
Davies EB; Parnovski L 《The Quarterly Journal of Mechanics and Applied Mathematics》1998,51(3):477-492
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E. B. Barmatov A. Yu. Bobrovsky D. A. Pebalk M. V. Barmatova V. P. Shibaev 《Journal of polymer science. Part A, Polymer chemistry》1999,37(16):3215-3225
A family of a new hydrogen-bonded complexes based on comb-shaped LC copolymers containing the monomer units of cyanobiphenyl derivative and n-alkyloxy-4-oxybenzoic acid with a chiral dopant on the base of 4-pyridinecarboxylic acid and L -menthol, was prepared. At concentrations of chiral groups 1–25 mol %, the induction of cholesteric phase was observed. Temperature dependences of selective light reflection wavelengths were studied, and helix twisting power was calculated. Depending on the type of copolymer nematic matrix, this value is changed in the range from 12.1 to 19.6 µm−1. It was shown that an increase of a distance between the chiral dopant and the main polymer chain results in a lower values of helix twisting power. With respect to optical properties, the chiral nematic phase in the hydrogen-bonded complexes is comparable to classical cholesteric copolymers, in which the chiral group is covalently bound to polymer chain. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3215–3225, 1999 相似文献
8.
E. B. Barmatov D. A. Pebalk M. V. Barmatova V. P. Shibaev 《Journal of polymer science. Part A, Polymer chemistry》2001,39(22):3953-3959
Liquid‐crystalline (LC) ionomers containing 2–15 mol % calcium ions were synthesized by the exchange reaction between the nematic LC copolymer, bearing oxycyanobiphenyl mesogenic groups, and the carboxyl groups of acrylic acid, with calcium acetate. The incorporation of 2–3 mol % Ca ions in the LC copolymer leads to some rise in the clearing point and glass‐transition temperature. A further increase in the concentration of metal ions (>5 mol %) is accompanied by induction of the smectic A phase where clearing point and glass‐transition temperatures keep constant values. Phase behavior of the LC ionomers may be understood on the basis of a structural model that considers the dual role of calcium ions in a polymer matrix. Metal ions act as points of noncovalent electrostatic binding of the polymer chains and are capable of forming larger ionic associates (multiplets). The comparison of the phase behavior of sodium and calcium containing LC ionomers shows that the formation of ionic links may lead to the growth of structure defects suppressing a positive influence of charged groups on the mesophase clearing temperature. The orientation behavior of the LC ionomers in the magnetic field was studied. It was shown that the incorporation of calcium ions (3 mol %) in the LC copolymer matrix leads to the growth of orientation order parameter S of the nematic phase. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3953–3959, 2001 相似文献
9.
P. Holstein E. B. Barmatov D. Geschke M. Bender V. P. Shibaev 《Colloid and polymer science》2000,278(8):711-718
The aim of this work is to study in detail the orientational structure of liquid-crystalline polymers with different molecular
weight. The advantage of our approach is the use of broad-band 1H and 2H NMR spectroscopy for the analysis of the orientational order of the main-chain and mesogenic groups in conjunction with
small-angle neutron scattering results. Investigations of a series of partially deuterated side-chain polymers with methoxybenzylbenzoate
mesogenic groups have been carried out. The deuteration of the main chain enables separate access to order and orientation
effects of the side chain and the main chain. The molecular orientation of the substances investigated can be frozen in its
nematic phase below the glass-transition temperature. It is independent of the molecular weight, whereas the dynamics of the
director reorientation (rotational viscosity) in the nematic phase strongly depends on the molecular weight. The main-chain
deuterons provide powder spectra after orientation of the polymer in magnetic fields, indicating a very weak or lacking orientational
anisotropy. A complete decoupling of the main and the side group can be deduced.
Received: 15 September 1999 Accepted: 7 February 2000 相似文献
10.
A. P. Kovshik O. V. Magdysyuk S. G. Polushin E. B. Barmatov M. V. Barmatova E. I. Ryumtsev 《Polymer Science Series A》2010,52(2):119-125
Dielectric properties of a number of liquid-cry stalline comb-shaped copolymers with different ratios of side-chain mesogenic
cyanobiphenyl groups and acrylic acid units are studied. In the electric-field frequency range 300 Hz-100 MHz, temperature
dependences of dielectric permittivity are obtained for nematic and isotropic phases. The times of relaxation and the energies
of activation for processes responsible for dielectric-permittivity dispersion are measured. The quantitative relationship
between the dielectric characteristics and the content of acrylic acid units in the copolymer is established. 相似文献