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81.
The polymer reference interaction site model (PRISM) integral equation theory was used to describe the structure and thermodynamic properties of atactic polystyrene (aPS) melt, in which the monomer of aPS is represented with an eight-site model to characterize its microstructure. The intramolecular structure factors needed in the PRISM calculations were obtained from single chain MD simulations. The calculated results indicate that the results by the integral equation method agrees well with experiments, and can reflect the fine microscopic structure of real aPS melt. This work shows that the PRISM theory is a powerful tool for investigating the structure and properties of complex polymers. 相似文献
82.
Klára Melánová Ludvík Beneš Vítězslav Zima Jan Svoboda Miroslava Trchová Jiří Dybal 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):95-101
Intercalation compounds of α-Zr(HPO4)2 · H2O with 1,2-alkanediols (from C3 to C16) have been prepared by replacing 1-propanol in α-Zr(HPO4)2 · 2C3H7OH with the desired 1,2-alkanediols by a treatment in a microwave field. It was found that the intercalates contain 1.5 molecules
of diol per formula unit. The diol molecules are placed between the host layers in a bimolecular way with their aliphatic
chains tilted at an angle of 51°. The diol molecules are anchored in the interlayer space by H-bonds. A mixed intercalate,
containing 1,2-butanediol and 1,2-decanediol in a roughly equimolar ratio, is formed when the α-Zr(HPO4)2 · 2C3H7OH intercalate, suspended in a mixture of 1,2-butanediol and 1,2-decanediol, is exposed to microwave radiation. No new phase
containing both types of the guest molecules was observed when the 1-propanol intercalate, suspended in a mixture of 1-propanol
and 1,2-octanediol, is exposed to microwave radiation. 相似文献
83.
I. E. Animitsa N. A. Kochetova S. S. Nokhrin E. N. Dogodaeva 《Russian Journal of Electrochemistry》2007,43(6):699-707
Synthesis of (Sr, Ba)4Э2Nb2O11 ± δ where E = Mn, Cr, Cu and solid solution (Sr1?y Cuy)6 ? 2x Nb2 + 2x O11 + 3x is performed. By measuring the overall conductance of some solid-solution compositions it is established that the conductance increases with the cubic-lattice parameter and concentration of oxygen vacancies. Values of the conductance in humid air at T < 700°C are shown to increase as compared with dry air. Mass spectrometry analysis confirms the possibility of water incorporation into the complex-oxide structure out of a gas phase. Complex certification of samples of the composition (Sr, Ba)4E2Nb2O11 where E = Mn, Cr, Cu is performed. It is established that the decrease in the overall electroconductance occurs in the series Sr4Mn2Nb2O11 > Ba4Mn2Nb2O11 > Sr4CrMnNb2O11 > Sr4Cu2Nb2O11. Investigation of the overall electroconductance in dry and moist atmospheres shows that the effect of humidity exerts no influence on the values of the overall electroconductance. The oxygen-ion constituent of conductance is determined by the Arzhannikov method and is also evaluated from a σ,pO2 dependence. It is established that the presence of an element with a variable oxidation degree for compositions of the type Sr4E2Nb2O11 leads to an increase in the contribution made by the electronic constituent. In so doing, the magnitude of the oxygen-ion conductance practically does not alter. Thermal and mass spectrometry analyses show that, for the Sr4E2Nb2O11 compositions where E = Mn, Cr, Cu, there occurs no water intercalation into structure, correspondingly, there is observed no appearance of a protonic constituent of conduction. 相似文献
84.
85.
1 INTRODUCTION Bauxite porcelain is a novel “K2O–Al2O3–SiO2” system ceramic by using sintered bauxite, clay and potash feldspar and albite as the main raw materials with the Al2O3’s content of 50%~60(massfraction). Compared to the traditional“K2O–Al2O3–SiO2” feldspar porcelain by using quartz, bolus alb and potash feldspar and albite as the main raw materials, the bauxite porcelain possesses such advantages as high mechanical strength, excellent electrical insula- tion prop… 相似文献
86.
Youngjae Yoo Changhyun Park Jong Chan Won Sung‐Goo Lee Kil‐Yeong Choi Jae Heung Lee 《先进技术聚合物》2007,18(12):1015-1019
In this paper, we showed the simplified continuous process to crystallize the polycarbonate (PC) melts using sonocrystallization which is based on ultrasonic cavitation and ‘hot spot’ theory. High power ultrasonic wave was introduced to crystallize the PC prepolymers which is generally used for solid‐state polymerization (SSP) to obtain the ultra‐high molecular weight PCs. The structure and properties of PC treated with ultrasonic wave such as torque changes and crystallinities were studied. The experimental results showed that ultrasonic wave could improve the crystallinities of PCs and sonication time was proportional to their crystallinity. This is attributed to the decrease of the specific volume and the resulting shrinkage is compensated by a flux of a polymer melt toward the crystallization front. Torque data were collected directly from the Haake internal mixer and crystallinities were evaluated from differential scanning calorimeter (DSC). This process is an environmentally benign process so that no additional solvents or treatments are needed and will be very useful in the conventional solid‐state process which is used industrially. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
87.
The effect of sintering dispersed and bulk, low molecular weight (Mn = 50,000 Da), nano-emulsion polytetrafluoroethylene (PTFE) particles near their melting point is described. With the nascent particles consisting of ca.75 nm diameter, hexagonal, single crystals, sintering at, e.g., 350℃, results, initially, in merger of neighboring particles,followed by individual molecular motion on the substrate and the formation of folded chain, lamellar single crystals and spherulites, and on-edge ribbons. It is suggested these structures develop, with time, in the mesomorphic "melt". Sintering of the bulk resin yields extended chain, band structures, as well as folded chain lamellae; end-surface to end-surface merger,possibly by end-to-end polymerization, occurs with increasing time. 相似文献
88.
Jodie N. Haigh Ya‐mi Chuang Brooke Farrugia Richard Hoogenboom Paul D. Dalton Tim R. Dargaville 《Macromolecular rapid communications》2016,37(1):93-99
A new method for fabricating hydrogels with intricate control over hierarchical 3D porosity using microfiber porogens is presented. Melt electrospinning writing of poly(ε‐caprolactone) is used to create the sacrificial template leading to hierarchical structuring consisting of pores inside the denser poly(2‐oxazoline) hydrogel mesh. This versatile approach provides new opportunities to create well‐defined multilevel control over interconnected pores with diameters in the lower micrometer range inside hydrogels with potential applications as cell scaffolds with tunable diffusion and transport of, e.g., nutrients, growth factors or therapeutics.
89.
Natalia Castro Christine Raynaud Antoine Rouilly Luc Rigal Christian Quellet 《高分子科学杂志,C辑:聚合物评论》2016,56(1):137-186
Encapsulation of flavor and aroma compounds has been largely explored in order to meet appraisal demands from consumers by improving the impact of flavor during the consumption of food products. Even though several techniques have been used for encapsulating volatile compounds, i.e., spray drying, fluidized bed coating, coacervation, and melt extrusion, those most frequently used in the food industry are spray drying and melt extrusion. In this article, the different techniques of encapsulation of flavors and fragrances in polymer-based matrices by extrusion are reviewed and partly re-defined, emphasizing the differences between the various techniques reported so far and the role of matrix types, additives, and operative conditions. Also, the role of water as a key parameter for controlled release and shelf stability of the delivery system will be discussed. 相似文献
90.
Enhanced Catalytic Hydrogen Evolution Reaction in Phosphorene Nanosheet via Cobalt Intercalation 下载免费PDF全文
Searching alternatives to Pt-based catalyst for producing hydrogen via water splitting has gathered enormous attention to develop renewable energy. Phosphorene has been investigated widely for its large surface area, low cost, and high carrier mobility, however, the poor activity in hydrogen evolution reaction (HER) and low conductivity limit its practical application. Herein, on the basis of first-principles calculations, we demonstrate that the catalytic HER in phosphorene can be enhanced significantly with cobalt intercalations. The Co-intercalated phosphorene is metallic with charge transfer from Co atoms to phosphorene, which could enhance the catalytic activity of phosphorene. In addition, the calculated Gibbs free energy of hydrogen adsorption on Co-intercalated phosphorene bilayer is comparable to that on Pt(111) surface, independent of the degree of hydrogen coverage. Our study implies that the Co intercalation provides an effective approach to enhance the catalytic HER inphosphorene. 相似文献