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991.
Rupasree R. Das Shashadhar Samal Seok‐Ju Choi Kurt E. Geckeler 《Macromolecular rapid communications》2001,22(11):850-854
The synthesis of a novel highly swelling, macroporous hydrogel from poly(allylamine) using 3‐chloropentan‐2,4‐dione as a crosslinker is reported. The swelling of the hydrogel was sensitive to changes in pH, temperature, and the extent of crosslinking. The dry gel exhibited a regular honeycomb network with smooth macropores. The hydrogel was inherently luminescent, and so was a metal polychelate. 相似文献
992.
993.
Alexander Steblyanko Wonmun Choi Fumio Sanda Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(13):2375-2380
A bifunctional five‐membered cyclic carbonate was synthesized from carbon dioxide and diglycidyl terephthalate, and its polyaddition with alkyl diamines were carried out in DMF at room temperature to obtain the corresponding poly(hydroxyurethane)s with Mn s in the range of 6300–13200 in good yields. The structures of the obtained polymers were confirmed by IR and NMR spectroscopy and their glass‐transition and decomposition temperatures were observed at 3–29 °C and 182–277 °C, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2375–2380, 2000 相似文献
994.
Young Gun Ko Ung Su Choi Byeng Gil Ahn Dong June Ahn 《Journal of polymer science. Part A, Polymer chemistry》2000,38(15):2815-2823
High‐performance materials for flameproofing, phosphates (polyphosphate and ammonium phosphate) were synthesized on viscose rayon felt. This surface reaction has the advantage of a nonblooming effect and an application in thermosetting plastics. Metal complexes have the effect of reducing the amount of smoke. Therefore, in the second step, transition‐metal complexes were synthesized on the viscose rayon ammonium phosphate felt. This article focuses on the surface modification of phosphates and metal complexes on viscose rayon. All reactions were confirmed by attenuated total reflectance Fourier transform infrared and time‐of‐flight secondary ion mass spectrometry. As the concentrations of phosphoric acid and urea increased, the peak intensities of ammonium ion groups and phosphate groups greatly increased. The thermal properties of the synthesized materials were studied with thermogravimetric analysis and oxygen index testing. On the basis of the experimental results, the synthesized flame‐retardancy materials showed excellent physicochemical and thermal effects and flame retardancy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2815–2823, 2000 相似文献
995.
996.
Polyhydroxyalkanoates (PHAs) are carbon and energy reserve material accumulated by numerous microorganisms and have been drawing much attention as biodegradable substitutes for conventional nondegradable plastics and elastomers. There are a number of different PHAs having a variety of material properties based on the different monomer composition. Poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) are now efficiently produced by bacterial fermentation at reasonable production costs. Recent advances in the production of short‐chain‐length (SCL) PHAs by bacterial fermentation are reviewed. Current status of the production of medium‐chain‐length (MCL) PHAs and SCL‐MCL‐PHA copolymers is also reviewed. 相似文献
997.
Diethylaminoethyl–chitin (DEAE–chitin) was synthesized by introducing DEAE groups onto the C(6)–OH in chitin. DEAE–chitin was N-deacetylated by heating in aqueous 10% sodium hydroxide containing sodium borohydride to prepare the diethylaminoethyl–chitosan (DEAE–chitosan). In addition, DEAE–chitin was quaternized with ethyl halide to produce triethylaminoethyl–chitin (TEAE–chitin). Their antibacterial activities were evaluated by using colony count against Staphylococcus aureus and Escherichia coli by means of shake flask method. The antibacterial activity was found to increase in order of DEAE–chitin, DEAE–chitosan, TEAE–chitin. DEAE–chitin was hydrolyzed by enzymes to investigate the effect of molecular weight on its antibacterial activities. The antibacterial activity was dependent on the structure, particularly on the molecular weight of chitin derivatives. © 1997 John Wiley & Sons, Ltd. 相似文献
998.
Particles of semiconducting polyaniline and a copolyaniline bearing ionic substituents were synthesized. Electrorheological (ER) fluids using these particles were compared with each other with respect to their rheological properties and dielectric spectra. In the steady shear rheological experiment conducted at 3 kV/mm (DC) at 25°C, the copolymer system showed higher stress than the polyaniline system in the whole shear rate region. This result was interpreted in terms of the conductivities of the particles and their dielectric spectra. Especially, the different behavior in the high shear rate region can be related to the electrical relaxation phenomena observed in the dielectric spectra. 相似文献
999.
An accurate and robust Navier–Stokes procedure to predict the complex flow about an aerofoil has been developed. Much improvement over existing methods is achieved in various aspects of the solution procedure. The computational grid generated by conformal mapping, which is not only orthogonal but aligned with the inviscid streamlines, keeps the equations simple and minimizes the error due to false diffusion. Formal second-order accuracy is ensured by employing the QUICK scheme for the convective derivatives in the full Navier–Stokes and turbulence transport equations. To treat the separated region properly and to better resolve the flow field in the wake, the two-layer k–ε turbulence model is incorporated. The onset of transition is triggered in a unique fashion to warrant the smooth transition to turbulent flow. Sample calculations for various aerofoil sections show that the prediction is improved substantially over those by existing methods. The details of the flow extending to the wake, such as the surface pressure distribution, CLmax, the velocity fields and the Reynolds stress profiles, are found to be in excellent agreement with the data. © 1997 John Wiley & Sons, Ltd. 相似文献
1000.
In the present study, we investigated the structure-activity relationship of naturally occurring hesperetin derivatives, as well as the effects of their glycosylation on the inhibition of diabetes-related enzyme systems, protein tyrosine phosphatase 1B (PTP1B) and α-glycosidase. Among the tested hesperetin derivatives, hesperetin 5-O-glucoside, a single-glucose-containing flavanone glycoside, significantly inhibited PTP1B with an IC50 value of 37.14 ± 0.07 µM. Hesperetin, which lacks a sugar molecule, was the weakest inhibitor compared to the reference compound, ursolic acid (IC50 = 9.65 ± 0.01 µM). The most active flavanone hesperetin 5-O-glucoside suggested that the position of a sugar moiety at the C-5-position influences the PTP1B inhibition. It was observed that the ability to inhibit PTP1B is dependent on the nature, position, and number of sugar moieties in the flavonoid structure, as well as conjugation. In the kinetic study of PTP1B enzyme inhibition, hesperetin 5-O-glucoside led to mixed-type inhibition. Molecular docking studies revealed that hesperetin 5-O-glucoside had a higher binding affinity with key amino residues, suggesting that this molecule best fits the PTP1B allosteric site cavity. The data reported here support hesperetin 5-O-glucoside as a hit for the design of more potent and selective inhibitors against PTP1B in the search for a new anti-diabetic treatment. 相似文献