Synthesis of new thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing epoxide pendant groups

A new class of thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing pendant epoxide groups were synthesized and characterized. These new epoxy polymers were prepared through the bromination of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in halogenated aromatic hydrocarbons followed by a Wittig reaction to yield vinyl‐substituted polymer derivatives. The treatment of the vinyl‐substituted polymers with m‐chloroperbenzoic acid led to the formation of epoxidized poly(2,6‐dimethyl‐1,4‐phenylene oxide) with variable pendant ratios, and the structures and properties were studied with nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The ratios of pendant functional groups were tailored for the polymer properties, and the results showed that the glass‐transition temperatures increased as the benzylic protons were replaced by bromo‐, vinyl‐, or epoxide‐functional groups, whereas the thermal stability decreased in comparison with the original polymer. Within a molar fraction of 20–50%, the degree of functionalization had little effect on the glass‐transition temperature; however, it correlated inversely with the thermal stability of each functionalized polymer. The thermal curing behavior of the epoxide‐functionalized polymer was enhanced by the increment of the pendant functionality, which resulted in a significant increase in the glass‐transition temperature as well as the thermal stability after the curing reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5875–5886, 2006     

Synthesis and characterization of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids with a branched-acyl chain

We previously reported the chemical synthesis of a series of novel monoacylated vitamin C derivatives, 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) possessing a straight-acyl chain of varying length from C(4) to C(18), as effective skin antioxidants. In this paper, we describe branched type of 6-Acyl-AA-2G derivatives (6-bAcyl-AA-2G) synthesized by use of a 2-branched-chain fatty acid anhydride as an acyl donor. The stability of 6-bAcyl-AA-2G in neutral solution was much higher than that of 6-Acyl-AA-2G, while they were susceptible to enzymatic hydrolysis for exerting vitamin C effect. These branched derivatives as well as 6-Acyl-AA-2G increased the radical scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl and the lipophilicity in octanol/water-partitioning systems with increasing length of their acyl group. In addition, the 6-bAcyl-AA-2G derivative with an acyl chain of C(12), 6-bDode-AA-2G had the excellent solubility to various solvents, suggesting easy handling in cosmetic use. These characteristics of 6-bAcyl-AA-2G may be available for skin care application as an effective antioxidant.     

金刚石生长的高压溶剂中碳的输运及其影响

 实验证实，在金刚石生长的高温超高压溶剂中，碳原子通过溶解扩散而输运，并清楚地看到在溶剂中也有对流现象。而宏观的对流现象的存在及其对金刚石生长的影响是不可忽视的。     

Two-dimensional intrinsic ferromagnetism at nitride-boride interfaces

We predict theoretically novel two-dimensional interface ferromagnetism at AlN/MgB(2)(0001) using first-principles calculations, where the interface is employed as an ordered structure of spin sites instead of point defects. Although N dangling bonds are apparently saturated, interfacial states exhibit spin polarization. Hund's coupling of the two N p(∥) orbitals as well as low density of states at the Fermi energy contribute to strong band ferromagnetism. Furthermore, first-principles electron transport calculations demonstrate that this interfacial spin polarization is responsible for quantum spin transport. The magnetization can be controlled by applied gate bias voltages.     

An Enzyme-Bound Bisubstrate Hybrid Inhibitor of Adenylosuccinate Synthetase

Two relatively weak herbicides, hydantocidin phosphate and hadacidin were linked by a C(3) chain to afford a potent inhibitor (the 2S hybrid is shown) of the enzyme adenylosuccinate synthetase. The crystal structures of the bisubstrate-enzyme complexes were determined.     

Self-consistent density functional calculation of field emission currents from metals

We have developed a fully self-consistent method which is suitable to examine field emission currents, on the basis of the density functional theory. In our method, the nearby counterelectrode is not necessary. By using this method, we have investigated field emission currents from a biased metallic surface represented by the jellium model. We have found that the energy barrier between the jellium and vacuum becomes lower than the Fermi energy under strong electric fields (e.g., 10 V/nm for r(s) = 4 bohr). In this situation, the slope of the Fowler-Nordheim plot becomes flatter than that under a weaker field.     

A synthesis and some reactions of 2-thiocyanato-2-ethylenic carbonyl compounds

A synthesis of 2-thiocyanato-2-ethylenic carbonyl compounds was achieved by the reaction of epoxy ketones with Ph₃P(SCN)₂ (TPPT). Some useful transformations of 2-thiocyanato-2-cyclohexenone to 2,3-disubstituted cyclohexanones and iminothiazolines are described.