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51.
[formula: see text] Iron salts efficiently catalyze the Doyle-Kirmse reaction of allyl sulfides with (trimethylsilyl)diazomethane and ethyl diazoacetate in dichloroethane at 83 degrees C. Competitive dimerization is less of a problem with (trimethylsilyl)diazomethane than with ethyl diazoacetate. Good results are obtained using only 1.5 equiv of (trimethylsilyl)diazomethane, even without slow addition. Phosphine ligands affect the kinetics, but not the diastereoselectivity. Dppe and BINAP lead to higher yields than dppp, but no enantioselection was detected with R-(+)-BINAP. 相似文献
52.
53.
In this note we completely describe the structure of algebraic semigroups S with Sx=S or Sx degenerate and xS=S or xS degenerate
for each x∈S. We then apply our results in characterizing the separately continuous multiplications on a topological space
whose only self-maps are either surjective or have degenerate image. In particular, we find that any locally compact Hausdorff
space with this property can admit only trivial separately continuous multiplications. Examples of spaces satisfying this
property are certain continua discovered by H. Cook [1]. The authors are indebted to Karl H. Hofmann and James T. Rogers for
conversations elucidating the topological implications of Theorem 1.
The second author supported by NSF Grant GP28655 相似文献
54.
55.
56.
S. Berglund 《Colloid and polymer science》1978,256(3):283
Ohne Zusammenfassung 相似文献
57.
58.
Ting Yang Hui Long Michael Malkoch E. Kristofer Gamstedt Lars Berglund Anders Hult 《Journal of polymer science. Part A, Polymer chemistry》2011,49(18):4044-4054
Considering the large number of applications for hydrogels, a better understanding of the relation between molecular structure and mechanical properties for well‐defined hydrogel is essential. A new library has been compiled of poly(ethylene glycol) polymers (PEG) of different length end functionalized with diallyl, dithiol, and dimethacrylate, and crosslinked with complementary trifunctional crosslinkers. In this study, the hydrogels were initially analyzed by FT‐Raman and NMR to study the conversion ratio of the functional groups. The effects of solvent type, solid content concentration, curing time and length of the PEG chains on the final leaching, swelling and tensile properties of the hydrogels were studied. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
59.
Failure criteria for polymers need to include effects from the stress state. For this reason, biaxial test results are of
interest. However, biaxial test methods usually require expensive equipment. In the test method presented here, a disk of
epoxy is bonded between a steel ring and a steel disk. The temperature is then lowered until fracture is observed. Experiments
were performed on three different glassy epoxy polymers. The biaxial stress state was analyzed by finite element analysis
and by an approximate analytical model. Experimental observations support the ability of the method to provide material property
data. An approximate analytical model was found sufficiently accurate for stress analysis and determination of the stress
state at failure. 相似文献
60.
L. Rueda A. Saralegi B. Fernández-d’Arlas Q. Zhou A. Alonso-Varona L. A. Berglund I. Mondragon M. A. Corcuera A. Eceiza 《Cellulose (London, England)》2013,20(4):1819-1828
Polyurethane/Cellulose nanocrystal (CNC) nanocomposites have been prepared by means of in situ polymerization using CNCs as precursors of polyurethane chains. Thermal, mechanical and morphological characterization has been analyzed to study the effect of CNC on the micro/nanostructure, which consisted of individualized nanocellulose crystallites covalently bonded to hard and soft segments of polyurethane. The incorporation of low CNC content led to a tough material whereas higher amount of CNC provoked an increase in soft and hard segments crystallization phenomenon. Moreover, from the viewpoint of polyurethane and polyurethane nanocomposites applications focused on biomedical devices, biocompatibility studies can be considered necessary to evaluate the influence of CNC on the biological behaviour. SEM micrographs obtained from cells seeded on top of the materials showed that L-929 fibroblasts massively colonized the materials surface giving rise to good substrates for cell adhesion and proliferation and useful as potential materials for biomedical applications. 相似文献