Thermoresponsive shuttling of rotaxane containing trichloroacetate ion

A thermoresponsive rotaxane shuttling system was developed with a trichloroacetate counteranion of an ammonium/crown ether-type rotaxane. Chemoselective thermal decomposition of the ammonium trichloroacetate moiety on the rotaxane yielded the corresponding nonionic rotaxane accompanied by a positional change of the crown ether on the axle. The rotaxane skeleton facilitated effective dissociation of the acid, markedly lowering the thermal decomposition temperature.     

Improvement of the physical properties of poly(methyl methacrylate) by copolymerization with N-pentafluorophenyl maleimide; zero-orientational and photoelastic birefringence polymers with high glass transition temperatures

Copolymers of N-pentafluorophenyl maleimide (PFPMI) with methyl methacrylate (MMA) were synthesized by a free radical initiator, such as AIBN. The refractive indexes of the copolymers remained nearly constant (1.4970 at 532 nm) regardless of the polymer composition. These copolymers also showed high thermal stability. The orientational and photoelastic birefringence of the copolymers obtained were measured. Since both of the orientational and photoelastic birefringences of PMMA are negative whereas poly(PFPMI) exhibits positive, thus we have obtained nearly zero orientational and photoelastic birefringence polymers when the ratios of MMA/PFPMI were 91.8/8.2 and 97.0/3.0 mol%, respectively. Based on the experimental data, the ratios of MMA/PFPMI for zero birefringence were determined to be 88.9/11.1 and 93.8/6.2 mol% for orientational and photoelastic birefringence, respectively. The Tgs of corresponding copolymers were estimated to be 128 and 122 ℃.     

Cascade reactions in crystals through cation-π-controlled reorientation on exposure to HCl gas

Exposure of 4-azachalcones to HCl gas produced the corresponding HCl salts with a head-to-tail stacked alignment, irradiation of which produced the corresponding syn-HT dimers with high regio- and stereoselectivities, thus showing the effectiveness of the cascade process in crystals.     

Evaluating Optical Quality of a Bifocal Soft Contact Lens in Near Vision Using a Shack–Hartmann Wavefront Aberrometer

To assess optical characteristics of bifocal soft contact lenses (BCLs) in use, we measured wavefront aberrations of human eyes, of eyes with a monofocal soft contact lens (MCL), and of eyes with a BCL. Modulation transfer functions (MTFs), Strehl ratios, and simulated images for far and near vision were produced with the measured aberrations. High order aberrations of subject 1 were significantly smaller than those of subject 2 (t-test, P = 0.001). We found that wearing the BCL improved the optical quality of an eye in subject 1, expressed as the horizontal MTF from 2 to 48 cycles per degree (cpd) for near vision and the Strehl ratio (t-test, P = 0.009 for Strehl ratio). But we did not find the same effect in subject 2. This difference may be due to the difference in the aberrations of the eyes of the two subjects.     

Strain induced grain boundary premelting in bulk copper bicrystals

In bulk bicrystals strain induced grain boundary premelting (SIGBPM) occurs when heavy screw dislocation pileup can be held up to a certain high temperature, approximately 0.6T _M, where T _M is the melting point of bulk material in Kelvin. SIGBPM occurs at grain boundaries to which new twist component is added due to the rotation of both component crystals toward opposite direction about the axis perpendicular to the grain boundary plane. At the original grain boundary, grain boundary sliding takes place due to this relative rotation. In f.c.c. metals with relatively low stacking fault energies such as copper, nickel, brass(30Zn) and silver, dislocations dissociate into partials. Therefore high density tangled dislocations introduced during plastic deformation hardly loose. If these dislocations can be held to high temperatures, SIGBPM is promoted. Formation of static or dynamic recrystallized grains suppresses SIGBPM itself and the propagation of grain boundary cracks formed by SIGBPM.     

Surface modification of a TiO2 film electrode prepared by the sol-gel method and its effect on photoelectrochemical behavior

The surface of a TiO₂ film electrode, about 1 μm thick, prepared by the sol-gel method, was modified by being additionally coated with about 0.1 μm thick TiO₂---SiO₂, TiO₂---ZrO₂ or TiO₂---Al₂O₃ films. The effect of the additional coating on the photoelectrochemical properties of a TiO₂ film electrode was investigated in detail. On addition of the second additive to TiO₂, the flat band potential was shifted toward negative potential for SiO₂ and positive potential for ZrO₂ and Al₂O₃, which is attributed to the change in the point of zero zeta potential (pzzp), not in the electron affinity (EA). However, enhancement in photocurrent was not observed for all the cases.     

Small-angle x-ray scattering of isotactic polystyrene

Isothermal crystallization process of isotactic polystyrene at 167°C has been studied by smallangle x-ray scattering. The observed SAXS intensities consist of the twophase lamellar structure component, the density fluctuation, and the foreign particle components. The profile of lamellar structure component remains unchanged during crystallization while its intensity increases with crystallization. The lamellar structure of isotactic polystyrene is investigated on the basis of the interface distribution function. An interface distribution function is obtained from the lamellar structure component after correcting the effect of the finite thickness of boundary regions between crystalline and amorphous phases. In order to obtain the structure parameters, the Gaussian correlation model is used, in which the correlation between the distributions of neighboring crystal and amorphous thicknesses is taken into account. Agreement is satisfactory between the experimental results and the calculations. The structure parameters of isotactic polystyrene are determined for isothermal crystallization at 167°C as follows: the average and the standard deviation of crystal thickness are 40 A and 10 A, respectively, those of amorphous thickness are 70 A and 23 A, and the standard deviation of long period is 31 A.     

Synthesis and hybridization properties of oligodeoxynucleotides incorporating 2-N-carbamoylguanine derivatives as guanine analogs

2-N-Carbamoyldeoxyguanosine and its derivatives were synthesized and incorporated into ODNs. The T_m analyses revealed higher selective base recognition ability of 2-N-carbamoylguanine than that of guanine. The new guanine analog must be useful for the development of functional oligodeoxynucleotides capable of precise base recognition.     

Immobilization of CdS nanoparticles formed in reverse micelles onto aluminosilicate supports and their photocatalytic properties

CdS nanoparticles, prepared in reverse micellar system, were immobilized onto thiol-modified aluminosilicate particles (ASSH) by a simple operation: addition of ASSH in the micellar solution and mild stirring. The resulting CdS nanoparticles-aluminosilicate composites (ASCdS) were used as photocatalysts for H2 generation from 2-propanol aqueous solution. The chemical properties of the aluminosilicate, such as affinity for water and other reactants, were found to affect the photocatalytic property of the CdS nanoparticles immobilized. Zeolite particles, having affinity for water and 2-propanol, gave a good ASCdS photocatalyst with respect to H2 generation.