Production of cellulose nanofibrils via an eco-friendly approach

Cellulose - Swelling of cellulose fibers facilitates the fibrillation process by mechanical treatment. In this study, potassium hydroxide (KOH)-urea (KUr) solution was investigated to swell fibers...     

Living copolymerization of ethylene/1‐octene with fluorinated FI‐Ti catalyst

Living copolymerization of ethylene and 1‐octene was carried out at room temperature using the fluorinated FI‐Ti catalyst system, bis[N‐(3‐methylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato] TiCl₂/dried methylaluminoxane, with various 1‐octene concentrations. The comonomer incorporation up to 32.7 mol % was achieved at the 1‐octene feeding ratio of 0.953. The living feature still retained at such a high comonomer level. The copolymer composition drifting was minor in this living copolymerization system despite of a batch process. It was found that the polymerization heterogeneity had a severe effect on the copolymerization kinetics, with the apparent reactivity ratios in slurry significantly different from those in solution. The reactivity ratios were nearly independent of polymerization temperature in the range of 0–35 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

RIEMANN BOUNDARY VALUE PROBLEMS WITH GIVEN PRINCIPAL PART

In this article, the authors discuss the Riemann boundary value problems with given principal part. First, authors consider a special case and give a classification of the solution class Rn by the way. And then, they consider the general case. The solvable conditions for this problem and its solutions is obtained when it is solvable.     

An efficient, stereoselective synthesis of the hydroxyethylene dipeptide isostere core for the HIV protease inhibitor A-792611

A stereoselective synthesis of the hydroxyethylene dipeptide isostere 1 is described. The route employs a substrate-directed kinetic protonation of an alpha/gamma-substituted lactone to afford the desired stereochemistry. A method for converting the diastereomerically enriched intermediate lactone to the ring-open form with retention of stereochemistry is demonstrated. A novel procedure for utilizing N,N-dibromo-5,5-dimethylhydantoin in Hofmann rearrangements is disclosed. This route was used to prepare amino alcohol 1, the core portion of the HIV protease inhibitor A-792611, in 46% yield from phenylalanine-derived epoxide 2.     

Tuning the electronic structures of semiconducting SiC nanotubes by N and NHx (x=1,2) groups

We investigate the stable configurations and electronic structures of silicon carbide nanotubes (SiCNTs) decorated by N and NHx (x=1,2) groups by using first-principles calculations. We find that these groups can be chemically incorporated into the network of SiCNTs in different ways, accompanied with the formation of N-C and N-Si bonds. The adsorbing energy of N and NHx (x=1,2) groups on (5,5) and (8,0) SiCNTs ranges from -1.82 to -7.19 eV. The electronic structures of SiCNTs can be effectively modified by these groups and display diverse characters ranging from semiconducting to semimetallic, depending on the chirality of SiCNTs as well as the way of the incorporation of these functional groups. The relationship between the electronic structures and the configurations of these functionalized SiCNTs is also addressed by performing projected density of states combined with Milliken population analysis. These results are expected to open a way to tune the electronic structures of SiCNTs which may have promising applications in building nanodevices.     

A new efficient visible-light-driven photocatalyst Na0.5Bi1.5VMoO8 for oxygen evolution

A new visible-light-driven photocatalyst Na_0.5Bi_1.5VMoO₈ was developed by making a solid solution of BiVO₄ and (NaBi)_0.5MoO₄. The prepared powders were confirmed crystallizing in the tetragonal scheelite crystal structure by the XRD patterns and Raman spectra. Different from that of the tetragonal BiVO₄, Na_0.5Bi_1.5VMoO₈ showed a high activity for photocatalytic O₂ evolution under visible light irradiation, which is even better than that of monoclinic BiVO₄, a well-known efficient visible-light-driven photocatalyst. The mechanism of the improved activity of Na_0.5Bi_1.5VMoO₈ was discussed.     

Unusual reaction of beta-hydroxy alpha-diazo carbonyl compounds with Cl3CCN/NaH and Rh(II)-catalyzed reaction of beta-trichloroacetylamino alpha-diazo carbonyl compounds

The hydroxyl group was directly converted into the trichloroacetylamino group by reacting beta-hydroxy alpha-diazo carbonyl compounds with Cl(3)CCN and NaH. Rh(II)-catalyzed reactions of the beta-amino alpha-diazo carbonyl compounds were discussed. [reaction: see text]     

Catalytic asymmetric [2,3]-sigmatropic rearrangement of sulfur ylides generated from copper(I) carbenoids and allyl sulfides

Catalytic asymmetric sulfur ylide [2,3]-sigmatropic rearrangement of carbenoids generated from aryldiazoacetates has been investigated with a number of chiral Rh(II) and Cu(I) catalysts, and moderately high enantioselectivity (52-78% ee) can be achieved with Cu(MeCN)(4)PF(6)/2,2'-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline].     

Fabrication of highly ordered polymer/graphite flake composite with eminent anisotropic electrical property

Highly ordered polyester/graphite flake composite has been fabricated via orienting the graphite flakes within a polymer matrix. The randomly dispersed graphite flakes in a polyester prepolymer were induced twice along the electric field direction, followed by the cross‐linking of the prepolymer. Scanning electron microscopy (SEM), X‐ray diffraction (XRD) analysis showed that the graphite flakes in the resulting composites were aligned parallel to each other. This structure anisotropy of the composite appeared to be a significant electrical anisotropic property with five to six orders of magnitude. Analysis showed that field‐induced torque caused by the polarization of graphite flakes undergone at electric field was a main force inducing the orientation of the graphite flakes. Copyright © 2008 John Wiley & Sons, Ltd.