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151.
Petersen C Bakulin AA Pavelyev VG Pshenichnikov MS Bakker HJ 《The Journal of chemical physics》2010,133(16):164514
We study the spectral and orientational dynamics of HDO molecules in aqueous solutions of different concentrations of tertiary butyl alcohol (TBA) and trimethylamine-N-oxide (TMAO). The spectral dynamics is investigated with femtosecond two-dimensional infrared spectroscopy of the O-H stretch vibration of HDO:D(2)O, and the orientational dynamics is studied with femtosecond polarization-resolved pump-probe spectroscopy of the O-D stretch vibration of HDO:H(2)O. Both the spectral and orientational dynamics are observed to show bimodal behavior: part of the water molecules shows spectral and orientational dynamics similar to bulk liquid water and part of the water molecules displays a much slower dynamics. For low solute concentrations, the latter fraction of slow water increases linearly as a function of solute molality, indicating that the slow water is contained in the solvation shells of TBA and TMAO. At higher concentrations, the fraction of slow water saturates. The saturation behavior is much stronger for TBA solutions than for TMAO solutions, indicating the aggregation of the TBA molecules. 相似文献
152.
Mesoscopic simulation of processes of drying and swelling of thin copolymer films on a solid substrate is performed. Structural rearrangements in films of symmetric and asymmetric diblock copolymers are studied by the dissipative particle dynamics method in the presence of both nonselective and selective solvents. The plasticizing effect of a solvent is favorable for formation of lamellar and hexagonal mesophases. Owing to evaporation of the solvent from a film or its absorption from the external volume, flows along the normal to the film surface arise. These flows exert an orienting effect on the microdomain structure. 相似文献
153.
M. V. Pavlov A. M. Balashov A. Yu. Ermilov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(10):1759-1766
The frontier molecular orbitals of [C n ] q hydrocarbons, fragments of (n, 0) nanotubes, were considered. Asymptotic estimates for two different sets of frontier molecular orbitals were obtained in the Hückel approximation. The problem was shown to be equivalent to the search for model polyene levels with alternating resonance parameters (β and β′ = γβ). The γ parameter was determined by the symmetry type of molecular orbitals and took on values from 0 to 2. The problem was reduced to an analysis of a regular linear polyene with a modified terminal atom by taking alternant symmetry into account. The states of the system were classified according to quasi-momentum Θ values, which could be complex. Solutions with a complex Θ value were localized at tube ends and could be interpreted as Tamm states. The criterion of the appearance of Tamm solutions for the problem under consideration was formulated, γ < 1 − 1/(q + 2). The conclusion was drawn that these states for an arbitrary [C n ] q fragment lied close to the Fermi level, and their energies were described by the asymptotic equation α ± βρ(q + 1). Delocalized levels were always situated farther from the Fermi level than Tamm states. 相似文献
154.
G. M. Pavlov G. F. Kolbina I. I. Gavrilova E. F. Panarin 《Polymer Science Series A》2010,52(2):115-118
For samples of various molecular masses, the flow birefringence of poly(styrene-4-sulfonate sodium) macromolecules in aqueous
solutions at various ionic strengths is studied in relation to the concentration of NaCl. It is shown that the sign of birefringence
changes from negative to positive with an increase in the ionic strength of a solution. Application of the macroform theory
to the Maxwell effect makes it possible to estimate the intrinsic optical anisotropy of the repeating unit of poly(styrene-4-sulfonate
sodium) (a||- a⊥) = −17 × 10-25 cm3), which nearly coincides with similar values known for atactic polystyrene and poly(κ-methylstyrene). 相似文献
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159.
Sokolov MN Gushchin AL Abramov PA Virovets AV Peresypkina EV Fedin VP 《Inorganic chemistry》2007,46(11):4677-4682
New ternary and quaternary molybdenum cluster chalcohalides were obtained by high-temperature reactions between Mo, chalcogens, and halogens in evacuated ampules. The crystal structures of [Mo3Se7(TeBr3)Br2]2[Te2Br10] (1), [Mo3Se7(TeI3)I2]I (2), and [Mo3Te7(TeI3)3]2(I)(TeI3) (3) were determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of positively charged zigzag chains infinity1 [Mo3Se7(TeX3)X4/2] (X=Br, I), with Te2Br102- and I-, respectively, as counterions. The TeI3- and TeBr3- ions function as bidentate ligands in 1 and 2. In 3, TeI3- is not coordinated to the metal but acts as a counterion to the [Mo3Te7(TeI3)3]+ cluster cation. 相似文献
160.
Sokolov MN Gushchin AL Kovalenko KA Peresypkina EV Virovets AV Sanchiz J Fedin VP 《Inorganic chemistry》2007,46(6):2115-2123
The reaction of aqueous [W3S7(C2O4)3](2-) with Ln(3+) and Th(4+) in a 1:1 molar ratio leads to oxalate-bridged heteropolynuclear molecular complexes and coordination polymers. La(3+) and Ce(3+) give a layered structure with big (about 1.8 nm) honeycomb pores which are filled with water molecules and lanthanide ions, in {[Ln(H2O)6]3[W3S7(C2O4)3]4}Br x xH2O (Ia and Ib). The smaller Pr(3+), Nd(3+), Sm(3+), Eu(3+), and Gd(3+) ions give discrete nanomolecules [(W3S7(C2O4)3Ln(H2O)5)2(mu-C2O4)] (with a separation of about 3.2 nm between the most distant parts of the molecule), which are further united into zigzag chains by specific S2...Br- contacts to achieve the overall stoichiometry K[(W3S7(C2O4)3Ln(H2O)5)2(mu-C2O4)]Br.xH2O (IIa-IId). Th(4+) gives K2[(W3S7(C2O4)3)4Th2(OH)2(H2O)10] x 14.33H2O (III) with a nanosized discrete anion (with a separation of about 2.7 nm between the most distant parts of the molecule), in which two thorium atoms are bound via two hydroxide groups into the Th2(OH)2(6+) unit, and each Th is further coordinated by five water molecules and two monodentate [W3S7(C2O4)](2-) cluster ligands. All compounds were characterized by X-ray structure analysis and IR spectroscopy. Magnetic susceptibility measurements in the temperature range of 2-300 K show weak antiferromagnetic interactions between two lanthanides atoms for compounds IIa, IIb, and IId. The thermal decomposition of Ia, Ib, and IIb was studied by thermogravimetry. 相似文献