共查询到20条相似文献,搜索用时 15 毫秒
1.
The hollow composite spheres with a raspberry‐like structure were prepared by a self‐assemble heterocoagulation based on the inter‐particle hydrogen‐bonding interaction between the amide groups of hollow poly (N,N′‐methylenebisacrylamide‐co‐N‐isopropyl acrylamide) (P(MBA‐co‐NIPAAm)) microspheres and the carboxylic acid groups of poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA)) nanoparticles, in which P(EGDMA‐co‐MAA) nanoparticle acted as the corona and the hollow P(MBA‐co‐NIPAAm) microsphere behaved as the core. The control coverage of the corona particles on the surface of hollow core microspheres of P(MBA‐co‐NIPAAm)/P(EGDMA‐co‐MAA) hollow composite sphere was studied in detail through adjustment of the mass ratio between the core and corona particles. The effect of the pH on the stability of the raspberry‐like hollow spheres was investigated. The polymer particles and the resultant heterocoagulated raspberry‐like hollow spheres were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The dependence of the particle size of a polyacrylate core-shell emulsion on temperature has been investigated in the temperature range of 10–55°C by photon correlation spectroscopy. To compare, the dependence of the particle size of an aqueous suspension of a polystyrene standard on temperature has been also investigated under the same conditions. This showed that as the temperature increases, the particle size of both samples decreases, but the rate of size decrease of the polystyrene standard is larger than that of the polyacrylate core–shell emulsion. By linear regression analysis, two regression equations of both samples have been set up. Furthermore, the apparent moving activation energy has been worked out from the size–temperature data. 相似文献
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Michal Kedem Shlomo Margel 《Journal of polymer science. Part A, Polymer chemistry》2002,40(9):1342-1352
Polystyrene template microspheres of 1.4 ± 0.1 μm were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2‐methoxy ethanol. These template particles were then swelled at room temperature in a single step with emulsion that was prepared in sodium dodecyl sulfate aqueous solution from a swelling solvent (dibutyl phthalate) containing the initiator (benzoyl peroxide) and monomer(s) (chlormethylstyrene, divinylbenzene, or ethylene dimethacrylate). Composite uniform particles composed of the template polystyrene and noncrosslinked or crosslinked polychloromethylstyrene were prepared by polymerizing the monomer(s) within the swelled particles at 73 °C. Crosslinked uniform polychloromethylstyrene particles of higher surface area were formed by dissolving the template polystyrene polymer of the composite particles. The influence of various reaction parameters, such as dibuthyl phthalate concentration, chloromethylstyrene concentration, crosslinker type and concentration, and so forth on the molecular weight, size, size distribution, shape, morphology, surface area, and decomposition temperature of the particles was investigated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1342–1352, 2002 相似文献
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Raymond Joso Stefan Reinicke Andreas Walther Holger Schmalz Axel H. E. Müller Leonie Barner 《Macromolecular rapid communications》2009,30(12):1009-1014
We present a facile access route to hydroxy‐functional narrow disperse microspheres of well‐defined grafting density (GD). Ethylene oxide has been grafted from highly crosslinked poly(divinyl benzene) microspheres by anionic ring‐opening polymerization using sec‐butyllithium as activator together with the phosphazene base t‐BuP4. Initially, core microspheres have been prepared by precipitation polymerization utilizing divinyl benzene (DVB, 80 wt.‐%). The grafting of poly(ethylene oxide) (PEO) from the surface resulted in the formation of functional core–shell microspheres with hydroxy‐terminal end groups. The number average particle diameter of the grafted microspheres was 3.6 µm and the particle weight increased by 5.7%. The microspheres were characterized by SEM, FT‐IR spectroscopy, elemental analysis, and fluorescence microscopy. The surface GD (determined via two methods) was 1.65 ± 0.06 and 2.09 ± 0.08 chains · nm−2, respectively.
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An emulsifier‐free core–shell polyacrylate emulsion, containing nano‐SiO2 nanoparticles in the core and diacetone acrylamide (DAAM) in the shell, has been successfully prepared by emulsifier‐free seeded emulsion polymerization. The effects of reaction temperature, dropping time, nano‐SiO2 and initiator contents, and variation of the composition of core monomers on the amount of coagulum, particle size, and monomer conversion have been investigated. The particle morphology and the distribution of emulsion particles have been measured by transmission electron microscopy (TEM) and dynamic light scattering. The keto‐carbonyl groups on the surface of the polyacrylate emulsion nanoparticles reacted with adipic dihydrazide (ADH) to form a film with a cross‐linked network structure at room temperature. Therefore, the emulsifier‐free core–shell emulsion could be used as a two‐component room temperature curable waterborne coating. It was also found that the properties of the coating were clearly superior after using the cross‐linker. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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This article presents experimental studies of (a) X‐ray absorption, (b) particle orientation, and (c) the shear viscosity of ternary talc–calcite–polystyrene compounds. A quantitative investigation of X‐ray absorption using a wide‐angle X‐ray diffraction (WAXD) intensity method for binary mixture (PS/talc, PS/calcite) systems and ternary mixtures (PS/talc/calcite) systems is reported. The Alexander–Klug equation was used to interpret the data. X‐ray diffraction pole figures indicate that talc particles orient in shear flows perpendicular to the direction of shear with their surfaces parallel to die/mold walls. There was a general tendency in mixed particle systems for the talc particles to decrease in orientation with increasing calcite content. The shear viscosity of the compounds was measured and found to increase with increasing particle loading and vary with particle composition. The talc, calcite, and talc/calcite‐filled thermoplastic melts at higher loadings were found by creep measurements to exhibit yield values, i.e., stresses below which there is no flow. We found a viscosity–shear stress plateau at low shear stress. The true yield values are much lower than yield values measured by extrapolation of higher shear stress data. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1787–1802, 1999 相似文献
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Birger Lange Nadine Metz Muhammad Nawaz Tahir Friederike Fleischhaker Patrick Theato Heinz‐Christoph Schrder Werner E. G. Müller Wolfgang Tremel Rudolf Zentel 《Macromolecular rapid communications》2007,28(20):1987-1994
Colloidal photonic crystals were prepared from monodisperse core–shell particles. The shell is hereby formed from a functional monomer, such as glycidylmethacrylate or different reactive ester monomers, which can perform chemical reactions and the core from a standard monomer, which yields highly monodisperse colloids. It was possible to crystallize the core–shell particles into artificial opals with excellent optical properties. Reactions on the functional surface of the colloids were carried out, which lead to a dramatic rise in the mechanical stability or to a functionalization of His‐tagged silicatein, which acts as nanoreactor to synthesize and immobilize gold nanoparticles from auric acid onto the core–shell colloids.
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An effective one‐pot, convenient process for the synthesis of 1‐ and 5‐substituted 1H‐tetrazoles from nitriles and amines is described using1,4‐dihydroxyanthraquinone–copper(II) supported on Fe3O4@SiO2 magnetic porous nanospheres as a novel recyclable catalyst. The application of this catalyst allows the synthesis of a variety of tetrazoles in good to excellent yields. The preparation of the magnetic nanocatalyst with core–shell structure is presented by using nano‐Fe3O4 as the core, tetraethoxysilane as the silica source and poly(vinyl alcohol) as the surfactant, and then Fe3O4@SiO2 was coated with 1,4‐dihydroxyanthraquinone–copper(II) nanoparticles. The new catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, thermogravimetric analysis, vibration sample magnetometry, X‐ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm analysis and inductively coupled plasma analysis. This new procedure offers several advantages such as short reaction times, excellent yields, operational simplicity, practicability and applicability to various substrates and absence of any tedious workup or purification. In addition, the excellent catalytic performance, thermal stability and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the catalyst could be magnetically separated and reused six times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Xuejun Cui Shuangling Zhong Haitao Zhang Qiang Gu Junfeng Li Hongyan Wang 《先进技术聚合物》2007,18(7):544-548
Polytetrafluoroethylene (PTFE)‐polyacrylate core–shell nanoparticles were produced by using PTFE micropowder and acrylate via seeded emulsion polymerization in the presence of fluorosurfactant. The properties of emulsion under various polymerization conditions were investigated and optimized. The chemical composition of the PTFE‐polyacrylate nanoparticles was characterized by Fourier‐transform infrared spectrometry (FTIR). The particle size and core–shell structure of the resulting PTFE‐polyacrylate nanoparticles were confirmed by transmission electron microscopy (TEM). Wettability of the PTFE‐polyacrylate core–shell particles was higher than the pristine PTFE. The formation of this kind of PTFE‐polyacrylate core–shell nanoparticles could improve the compatibility of PTFE with other materials because PTFE is covered by polyacrylate shell, which make them promising in various fields. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Lingnan Chen Birong Zeng Yueguang Wu Jianjie Xie Shirong Yu Conghui Yuan Weiang Luo Yiting Xu Lizong Dai 《先进技术聚合物》2014,25(9):1069-1076
Magnetic composite nanospheres (MCS) were first prepared via mini‐emulsion polymerization. Subsequently, the hybrid core–shell nanospheres were used as carriers to support gold nanoparticles. The as‐prepared gold‐loading magnetic composite nanospheres (Au‐MCS) had a hydrophobic core embed with γ‐Fe3O4 and a hydrophilic shell loaded by gold nanoparticles. Both the content of γ‐Fe3O4 and the size of gold nanoparticles could be controlled in our experiments, which resulted in fabricating various materials. On one hand, the Au‐MCS could be used as a T2 contrast agent with a relaxivity coefficient of 362 mg?1 ml S?1 for magnetic resonance imaging. On the other hand, the Au‐MCS exhibited tunable optical‐absorption property over a wavelength range from 530 nm to 800 nm, which attributed to a secondary growth of gold nanoparticles. In addition, dynamic light scattering results of particle sizing and Zeta potential measurements revealed that Au‐MCS had a good stability in an aqueous solution, which would be helpful for further applications. Finally, it showed that the Au‐MCS were efficient catalysts for reductions of hydrophobic nitrobenzene and hydrophilic 4‐nitrophenol that could be reused by a magnetic separation process. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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One‐Nanometer‐Precision Control of Al2O3 Nanoshells through a Solution‐Based Synthesis Route 下载免费PDF全文
Wei Zhang Zi‐Xiang Chi Wen‐Xin Mao Prof. Rong‐Wen Lv Prof. An‐Min Cao Prof. Li‐Jun Wan 《Angewandte Chemie (International ed. in English)》2014,53(47):12776-12780
Forming uniform metal oxide nanocoatings is a well‐known challenge in the construction of core–shell type nanomaterials. Herein, by using buffer solution as a specific reaction medium, we demonstrate the possibility to grow thin nanoshells of metal oxides, typically Al2O3, on different kinds of core materials, forming a uniform surface‐coating layer with thicknesses achieving one nanometer precision. The application of this methodology for the surface modification of LiCoO2 shows that a thin nanoshell of Al2O3 can be readily tuned on the surface for an optimized battery performance. 相似文献
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《Macromolecular rapid communications》2017,38(3)
Ruthenium‐functionalized poly(N‐isopropyl acrylamide)‐based chemically oscillating microgels with diameters between 1 and 6 µm are synthesized by a modified precipitation polymerization approach. It is found that the initial amount of N‐isopropyl acrylamide (NIPAAm) can significantly affect the final sizes of the microgels. 2.5 g of initial NIPAAm results in microgels with maximum average diameter of ≈6 ± 0.5 µm. Making use of their fluorescence due to their ruthenium contents and their larger sizes compared to microgels prepared using other traditional methods, the impact of changes in the NaBrO3 concentrations on their microscopic behavior is studied using a combination of fluorescence microscopy and dynamic light scattering techniques. When increasing the concentration of NaBrO3 in a solution, the microgels first experience a decrease in size followed by aggregation that leads to the loss of colloidal stability. Finally, the redox potential behavior and optical performance of the Belousov–Zhabotinsky reaction catalyzed by these microgels are studied by electrochemical and spectroscopic means.
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Sachin Rawalekar Sreejith Kaniyankandy Sandeep Verma Dr. Hirendra N. Ghosh 《Chemphyschem》2011,12(9):1729-1735
Herein, we report the synthesis of aqueous CdTe/CdSe type‐II core–shell quantum dots (QDs) in which 3‐mercaptopropionic acid is used as the capping agent. The CdTe QDs and CdTe/CdSe core–shell QDs are characterized by X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR‐TEM), steady‐state absorption, and emission spectroscopy. A red shift in the steady‐state absorption and emission bands is observed with increasing CdSe shell thickness over CdTe QDs. The XRD pattern indicates that the peaks are shifted to higher angles after growth of the CdSe shell on the CdTe QDs. HR‐TEM images of both CdTe and CdTe/CdSe QDs indicate that the particles are spherical, with a good shape homogeneity, and that the particle size increases by about 2 nm after shell formation. In the time‐resolved emission studies, we observe that the average emission lifetime (τav) increases to 23.5 ns for CdTe/CdSe (for the thickest shell) as compared to CdTe QDs (τav=12 ns). The twofold increment in the average emission lifetime indicates an efficient charge separation in type‐II CdTe/CdSe core–shell QDs. Transient absorption studies suggest that both the carrier cooling and the charge‐transfer dynamics are affected by the presence of traps in the CdTe QDs and CdTe/CdSe core–shell QDs. Carrier quenching experiments indicate that hole traps strongly affect the carrier cooling dynamics in CdTe/CdSe core–shell QDs. 相似文献
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Spacer length controlled highly thermo reversible polyurethane–urea based on polystyrene: synthesis and crystallization studies 下载免费PDF全文
Poly(urethane–urea) (PUU) is prepared using dihydroxy functionalized polystyrene having Mw 2000 g/mol, 1,6 hexamethylene diisocyanate and three different diamines (1,2‐ethylenediamine, 1,4‐butanediamine and 1,6‐hexamethylene diamine) by melt polymerization method. The synthesized copolymer is characterized by viscosity measurements, Fourier transform infrared (FT‐IR) spectroscopy, wide angle 2D‐X‐ray scattering (WAXS) and differential scanning colorimetry (DSC). The inherent viscosity of the polymers is found to be in the range of 0.4–0.5 dl/g, suggesting that the polymers are of high molecular weight. FT‐IR results conclude that the urea groups form both monodendate and bidendate assemblies. Temperature‐dependent FT‐IR and WAXS data confirm that the crystallinity of the copolymer is highly reversible and depends on the spacer length. DSC data also confirm that the crystallization pattern depends on the spacer length. The swelling behavior in water and the solubility of the polymer in chloroform are depending on the type of chain extender used in the PUU synthesis. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Yan Gao Jiasheng Fang Yiwei Zhang Chao Zhang Shuo Zhao Yuming Zhou Mengqiu Huang Xiaoli Sheng 《应用有机金属化学》2018,32(3)
A facile strategy is reported for the fabrication of Pt‐loaded core–shell nanocomposite ellipsoids (Fe2O3‐Pt@DSL) consisting of ellipsoidal Fe2O3 cores, double‐layered La2O3 shells and deposited Pt nanoparticles (NPs). The formation of the doubled‐shelled structure uses Fe2O3‐Pt@mSiO2 as template sacrificial agent and it involves the re‐deposition of silica and self‐assembly of metal oxide units. The preparation methods of double‐shelled metal oxides avoid repeated coating and etching and could be utilized to fabricate other shaped double‐shelled composites. Characterization results indicated that the Fe2O3‐Pt@DSL nanocomposites possessed mesoporous structure and tunable shell thickness. Moreover, due to the formation of Fe2O3 and La2O3 composites, Pt NPs can also be stabilized via deposition on chemically active oxides with a synergistic effect. Therefore, as a catalyst for the reduction of 4‐nitrophenol, Fe2O3‐Pt@DSL showed superior catalytic activity and reusability due to structural superiority and enhanced composite synergy. Finally, well‐dispersed Pt NPs were encapsulated into the void between the shell layers to construct the Fe2O3‐Pt@DSL‐Pt catalyst. 相似文献
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Aligned MoOx/MoS2 Core–Shell Nanotubular Structures with a High Density of Reactive Sites Based on Self‐Ordered Anodic Molybdenum Oxide Nanotubes 下载免费PDF全文
Bowen Jin Xuemei Zhou Li Huang Markus Licklederer Prof. Dr. Min Yang Prof. Dr. Patrik Schmuki 《Angewandte Chemie (International ed. in English)》2016,55(40):12252-12256
The present work demonstrates the self‐organized formation of anodic molybdenum oxide nanotube arrays. The amorphous tubes can be crystallized to MoO2 or MoO3 and be converted fully or partially into molybdenum sulfide. Vertically aligned MoOx/MoS2 nanotubes can be formed when, under optimized conditions, defined MoS2 sheets form in a layer by layer arrangement that provide a high density of reactive stacking misalignments (defects). These core–shell nanotube arrays consist of a conductive suboxide core and a functional high defect density MoS2 coating. Such structures are highly promising for applications in electrocatalysis (hydrogen evolution) or ion insertion devices. 相似文献