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21.
The relationship between the chemical structure of nematic liquid crystals and their pretilt angles 总被引:1,自引:0,他引:1
About 50 different additives in one or more of three different nematic mixtures have been investigated to clarify the relationship between the chemical structure of the liquid crystal and the pretilt angle on a polyimide surface. The pretilts found for cells have been explained within our recently proposed population distribution model. For compounds with cyano-groups at one end, we find that the in-plane order is governed both by the surface-mesogen interaction and by the relative strength of the intermolecular interactions in the nematic phase. This strength is nearly linear in alkyl chain length for the compounds investigated. Changes in the strength due to variations in the core of the molecules can be calculated easily by using group contributions from the known Parachors. The in-plane order can be treated as a simple product of the contributions from the liquid crystal and from the polyimide. Different polar end groups will give different angles between the surface and the optical axis of the individual mesogens in the first monolayer. The cyano-group gives the highest angle and alkyl groups the lowest. For nitro-compounds the dimers formed are so strongly bound that they do not break up at the surface. Nitro-compounds will thus act as dialkyl compounds. For dialkyl compounds the pretilt angles are dominated by the difference between the chain lengths at the two ends of the molecule. 相似文献
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23.
Control of viscoelasticity using redox reaction 总被引:1,自引:0,他引:1
Tsuchiya K Orihara Y Kondo Y Yoshino N Ohkubo T Sakai H Abe M 《Journal of the American Chemical Society》2004,126(39):12282-12283
The viscoelasticity of a fluid was tuned with the Faradaic reaction of (11-ferrocenylundecyl)trimethylammonium bromide (FTMA), a "redox-switchable" surfactant. An aqueous solution of the reduced form of FTMA exhibited a remarkable viscoelasticity in the presence of sodium salicylate (NaSal) because of the formation of three-dimensional entanglement of wormlike micelles. Electrolytic oxidation of FTMA caused the viscosity of the system to dramatically decrease and the elasticity to disappear. This drastic decrease in viscoelasticity arose from the disruption of wormlike micelles. This novel electrorheological phenomenon is expected to be applicable to ink for inkjet printers, the electrochemically controlled release of substances entrapped in wormlike micelles of FTMA, and fluid flow rate control using electric signals. 相似文献
24.
Y. Kondo M. Matsumura M. Kubota 《Journal of Radioanalytical and Nuclear Chemistry》1994,177(2):311-320
The acidity change and solid formation in a simulated high level liquid waste (HLLW) containing precipitate were experimentally examined, when the acidity was reduced from 2M to 0.5M by denitration or simple dilution. The acidity of the simulated HLLW containing precipitate could be adjusted from 2M to around 0.5M by means of denitration or dilution, as well as the case of simulated HLLW without precipitate. The precipitation fractions of Zr, Mo and Te during denitration decreased with increasing amount of the precipitate already contained in the simulated HLLW. The amount of solid formed in the dilute simulated HLLW also decreased with increasing amount of precipitate in the simulated HLLW. Two process flow sheets for preparing HLLW for transuranic elements extraction were developed. One was a denitration process and the other a dilution process. 相似文献
25.
A number of nitrato complexes of metals have been found to be adsorbed on DEAE-cellulose from mixed acetic acid-nitric acid media, although none can be adsorbed from aqueous nitric acid solutions. The distribution coefficients of Sc, Mo, La, Sm, W, Re, Bi, Th and U are given as functions of acetic acid and nitric acid concentrations (sometimes in the presence of hydrogen peroxide to prevent hydrolytic precipitation). For 25 other metals column adsorption behaviour is described for a 90% acetic acid-10% 7.6M nitric acid mixture. Favourable differences in the distribution coefficients allow useful separations such as FeMoW and USmMoBiTh, to be achieved. 相似文献
26.
A. Fukumi I. Endo T. Horiguchi Y. Ishida T. Kondo T. Kuwamoto H. Matsuzaki T. Nakamura T. Takahashi 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,42(4):243-249
Systematic study of hyperfine structures, Zeeman and Stark effects in Sm I is performed for the lowest 7G1-6 levels belonging to the configuration 4f 66s6p by atomic-beam laser spectroscopy with fluorescence detection. The hyperfine coupling constants of 7G2-6 levels are determined. From the Zeeman splittings for the 4f 66s 2 7F2-6 ? 4f 66s6p 7G2-6 transitions, g-values are determined for the 7G2.6 levels and the precision is improved by several orders of magnitude. From the Stark splittings for the 7F0-3 ? 7G1-3 transitions, tensor polarizabilities α 2(J) are determined for the upper 7G1-3 levels. Particularly for the 7G1 level (15 650.55 cm?1) which has close-lying opposite-parity level, the isotope dependence of α 2(J) is clearly observed for the first time. 相似文献
27.
Ishikawa A Takata T Kondo JN Hara M Kobayashi H Domen K 《Journal of the American Chemical Society》2002,124(45):13547-13553
A Ti-based oxysulfide, Sm(2)Ti(2)S(2)O(5), was studied as a visible light-driven photocatalyst. Under visible light (440 nm < or = lambda < or = 650 nm) irradiation, Sm(2)Ti(2)S(2)O(5) with a band gap of approximately 2 eV evolved H(2) or O(2) from aqueous solutions containing a sacrificial electron donor (Na(2)S-Na(2)SO(3) or methanol) or acceptor (Ag(+)) without any noticeable degradation. This oxysulfide is, therefore, a stable photocatalyst with strong reduction and oxidation abilities under visible-light irradiation. The electronic band structure of Sm(2)Ti(2)S(2)O(5) was calculated using the plane-wave-based density functional theory (DFT) program. It was elucidated that the S3p orbitals constitute the upper part of the valence band and these orbitals make an essential contribution to the small band gap energy. The conduction and valence bands' positions of Sm(2)Ti(2)S(2)O(5) were also determined by electrochemical measurements. It indicated that conduction and valence bands were found to have satisfactory potentials for the reduction of H(+) to H(2) and the oxidation of H(2)O to O(2) at pH = 8. This is consistent with the results of the photocatalytic reactions. 相似文献
28.
29.
Dehydrroxy-trans-resorcylide () was synthesized by efficient intramolecular alkylation of the protected cyanohydrin. The butadiene telomer obtained by the palladium catalyzed reaction of butadiene with acetic acid was used as a suitable block of the carbocycle. 相似文献
30.
Hiroki Nakamura Jiro Tanaka Nobuaki Nakashima Keitaro Yoshihara 《Chemical physics letters》1981,77(2):419-421
The photoionization of 8-anilino-1-naphthalenesulfonate in polar solvents occurs through a biphotonic process, as proved by nanosecond flash photolysis. A transient absorption of a charge transfer to solvent (CTTS) state is found with ≈10 ns life-time. The state is shown to be an intermediate of the photoionization process. 相似文献