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排序方式: 共有159条查询结果,搜索用时 46 毫秒
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Alena Yarysheva Dmitry Strel'tsov Sergey Malakhov Olga Arzhakova Larisa Yarysheva Alexandr Volynskii 《Polymer International》2020,69(7):627-634
This work addresses the phenomenon of the development of a patterned surface relief on polymer films via different modes of environmental crazing. Commercial films of semicrystalline poly(tetrafluoroethylene) (PTFE) and amorphous glassy poly(ethylene terephthalate) (PET) were subjected to tensile drawing in the presence of physically active liquid environments (carbon tetrachloride or aliphatic alcohols). The structure parameters and wettability of the modified films were studied by AFM, SEM, profilometer measurements and contact angle measurements. Environmental intercrystallite crazing of PTFE is accompanied by the development of an unstable structure with a high free surface, which experiences marked strain recovery upon unloading. As a result of the relief formation, PTFE hydrophobicity is enhanced (the water contact angle increases by 25°). Classical environmental crazing of PET films is accompanied by the formation of an anisotropic surface relief which is an assembly of crazes oriented perpendicular to the direction of tensile drawing, thus leading to the phenomenon of anisotropic wetting. The proposed approach for structural surface modification makes it possible to use the advantages of surface instability and spontaneous self‐organization of the polymer towards the development of a unique surface microrelief. © 2020 Society of Chemical Industry 相似文献
3.
An experimental study of the self-diffusion and nuclear magnetic relaxation of poly(amidoamine) dendrimers with hydroxyl surface groups (PAMAM-OH) dissolved in methanol over a wide range of concentration (?) is reported. It is shown that experimental concentration dependences of PAMAM-OH self-diffusion coefficients (D) can be reduced to the so-called generalized ? dependence. Over macromolecular concentration range studied, the generalized concentration dependence of PAMAM-OH D coincides with analogous curve obtained for poly(allylcarbosilane) dendrimers of high generations. This result confirms the existence of common regularities of the dendritic macromolecule self-diffusion, and their independence of the individual physicochemical and structural properties of dendrimer, solvent, and features of their interactions in the given systems. The concentration dependence of the PAMAM-OH diffusion also exhibits a clear signature of an inflexible molecule. 相似文献
4.
Separation of platinum-metal-based homogeneous catalysts was achieved by their conversion to complexes of functionalized phosphines of the general formulae R3-n
P[(CH2)
x
CO2H)]
n
, R = Me, Et, Ph,n = 1, 2, 3,x = 1, 2, and [(HO2CCH2)PCH2]2, followed by extraction of the complexes into aqueous phase. This approach to regeneration of platinum metals from reaction mixtures after carrying out homogeneously catalyzed reactions was demonstrated on 11 examples of various types of reactions with Ru, Rh, Pd, Os, Ir and Pt compounds as catalysts. 相似文献
5.
The CTmod toolkit is a set of C++ class libraries based on the CERN's application development framework ROOT. It uses the Monte Carlo method to simulate energy imparted to a CT-scanner detector array. Photons with a given angle-energy distribution are emitted from the X-ray tube approximated by a point source, transported through a phantom, and their contribution to the energy imparted per unit surface area of each detector element is scored. Alternatively, the scored quantity may be the fluence, energy fluence, plane fluence, plane energy fluence, or kerma to air in the center of each detector element. Phantoms are constructed from homogenous solids or voxel arrays via overlapping. Implemented photon interactions (photoelectric effect, coherent scattering, and incoherent scattering) are restricted to the energy range from 10 to 200keV. Variance reduction techniques include the collision density estimator and survival biasing combined with the Russian roulette. The toolkit has been used to estimate the amount of scatter in cone beam computed tomography and planar radiography. 相似文献
6.
Attempts to carry out the hydroformylation of allyldiethylamine homogeneously catalyzed by rhodium complexes led to unexpected formation of N,N,N,N-tetraethyl-1,4-diaminobutane and 4-(diethylamino)-1-butanole as final products. The role of the catalyst on the product formation and the reaction mechanism are briefly discussed. 相似文献
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Wenhao Xu Murong Wen Jingbo Yu Qihong Zhang Nikolay E. Polyakov Alexandr V. Dushkin 《Drug development and industrial pharmacy》2013,39(12):1924-1932
AbstractIn this study, complexes of kaempferol (KF) with polysaccharide arabinogalactan (AG) and disodium glycyrrhizinate (Na2GA) were prepared through mechanochemical technique to improve the solubility and bioavailability of KF. The physicochemical properties and the interactions of KF with AG/Na2GA were investigated through dissolution, SEM, XRD, and DSC studies. The reduction of particle sizes and destruction of crystal forms revealed the formation of solid dispersion which may have assisted the dissolution of the drug. The accelerated stability study showed higher stability for KF–Na2GA complex. In vivo pharmacokinetic study was performed to observe the plasma drug concentrations for KF complexes. Mechanochemical complexation of KF with AG/Na2GA improved the pharmacological activity as evident by the inhibitory potential of the complexes towards carbohydrate metabolic enzymes. In vivo studies were performed in STZ-induced diabetic mice, where the group treated with KF–AG complex showed better liver and kidney function and lower blood glucose levels than pure KF. Therefore, mechanochemical complexes of KF with polysaccharide or glycyrrhizate may serve as a promising formulation for the treatment of diabetes. 相似文献
9.
Alexandr Valentinovich Vinogradov Vladimir Valentinovich Vinogradov 《Journal of the American Ceramic Society》2014,97(1):290-294
Nowadays, it is a great challenge to synthesize crystalline TiO2 nanostructures using low‐temperature methods without annealing stage. Such an approach allows to perform functional and structural modification in the formed crystalline phase by thermally unstable compounds, such as biomaterials, MOFs, dye sets in situ, which was previously considered impossible. In this work, we have developed and analyzed the effect of acidic peptization on formation of highly photoactive titania crystallites in an aqueous solution using titanium tetraisopropylate as a precursor. Acids with different dissociation degrees in water were used as peptizing mediators to determine the effect of protonation on sol formation. The dip‐coating films were obtained with consequent drying of the sols via evaporation of the solvent. The as‐prepared catalysts were characterized by X‐ray diffraction, AFM microscopy, UV–V is spectroscopy, Brunauer–Emmett–Teller surface area. The aggregate size of TiO2 in the colloidal suspension solution was measured by dynamic light scattering. Photocatalytic activity of films was studied by decomposition of Rhodamine B dye. It is found that the size of colloids in an aqueous solution is proportional to the protonation degree of the surface of particles and does not depend on the [Ti4+]/[H+] ratio, and peptization under weakly acidic conditions leads to anisotropic rod‐like nanoparticles. The highest photocatalytic activity was exhibited by the TiO2–HCl‐based coatings, ~3.5 times higher than that of the Acet.‐prepared sample. 相似文献
10.