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91.
In situ graft copolymerization of polystyrene (PS) on polybutadiene (PB) during polymerization of PB solution in styrene monomer was investigated to determine the performance of grafting process, chain structure of generated copolymers, and their effectiveness as compatibilizing agents for incompatible PS-rich and PB-rich phases. The amount of copolymers and their chain structures at different stages of polymerization were determined by gel permeation chromatography (GPC) curves of the reactive blends (taken directly from the reaction) and physical blends (physically prepared based on total composition of reactive blends). It was demonstrated that copolymer formation started from the early stage of polymerization and continued up to the phase inversion stage. In addition, PS grafting on PB occurred initially via single-chain attachment and then converted to a double-chain scenario later on. Compatibilizing efficiency of the copolymers was evaluated by Huggins coefficient (k H) obtained by performing dilute solution viscometry (DSV) on samples taken at different stages of conversions. The effect of molecular weight of PB on the grafting process and the effectiveness of copolymers generated were also studied. It was found that while compatibilizing role of the copolymers produced from high molecular weight PB (HPB) increases as conversion goes further, the compatibilizing efficiency of the copolymers produced from low molecular weight PB (LPB) shows a very sharp variation in a small range of conversion. Plotting k H of physical blends against weight fraction of PB molecules in solid content of the solutions (w PB) showed negative deviation from mixture law with a W-like pattern containing two minima with a maximum in between. While a negative deviation was assumed as indication of immiscibility of the components, upward deviation at middle values of w PB was attributed to molecular segregations that reduce the interface between the incompatible PS-rich and PB-rich phases. 相似文献
92.
Akbar Zendehnam Mina Arabzadegan Sayed Mohsen Hosseini Nasrin Robatmili Sayed Siavash Madaeni 《Korean Journal of Chemical Engineering》2013,30(6):1265-1271
Polyvinylchloride-blend-styrene butadiene rubber based nanocomposite cation exchange membranes were prepared by solution casting technique. Iron-oxide nanoparticles and Ag-nanolayer were simultaneously utilized as filler and surface modifier in membrane fabrication. The effects of Ag-nanolayer film thickness on membrane physicochemical and antibacterial characteristics of nanocomposite PVC-blend-SBR/Iron-oxide nanoparticles were studied. SEM images showed membrane roughness decreasing by Ag nanolayer thickness increasing. Membrane charge density and selectivity declined by Ag nanolayer coating up to 5 nm in membranes and then showed increasing trend by more nanolayer thickness. Ionic flux also showed increasing trend. Membranes showed good ability in E-Coli removal. 20 nm Ag-nanolayer coated membrane showed better performance compared to others. 相似文献
93.
The contact time of particles at the walls of gas fluidized beds has been studied using a radioactive particle tracking technique to monitor the position of a radioactive tracer. The solids used were sand or FCC particles fluidized by air at room temperature and atmospheric pressure at various superficial velocities, covering both bubbling and turbulent regimes of fluidization. Based on the analysis of tracer positions, the motion of individual particles near the walls of the fluidized bed was studied. The contact time, contact distance and contact frequency of the particles at the wall were evaluated from these experimental data. It was found that in a bed of sand particles, the mean wall contact time of the fluidized bed of sand particles decreases by increasing the gas velocity in the bubbling and increases in the turbulent fluidization. In other words, the particle-wall contact time is minimum at the onset of turbulent fluidization in the bed of sand particles. However, the mean wall contact time is almost constant in both regimes of fluidization in the bed of FCC particles. All the existing models in the literature predict a decreasing contact time when the gas velocity in the bed is increased. It was also shown that the contact distance increases monotonously by increasing the gas velocity in the bed of sand particles, while it is almost constant for the bed of FCC particles. Contact frequency has a trend similar to that of the contact time for both sand and FCC particles. 相似文献
94.
This study investigated the effect of solubility of amphiphilic compounds of acidic crude oil in water on the surface and interfacial tension (IFT) with NaCl, MgCl2, CaCl2, and Na2SO4 salts. Accordingly, distilled water, along with the salts mentioned in zero ionic strength up to 2 mol were put in contact with crude oil to become saturated with amphiphilic compounds. The effects of these compounds were investigated on the properties of contact water by pH, total organic carbon (TOC), FTIR (Fourier transform infrared spectroscopy), water-air surface tension (ST), and water-n-decane IFT tests. The results showed that some of the organic components of crude oil, especially acidic and basic compounds, are present or soluble in water, which have a significant effect on reducing the surface and IFT. The IFT reduction of water-n-decane was greater than the water-air ST system. Also, the observations showed that for both NaCl and Na2SO4 salt water, with increasing ionic strength of water, there was an optimum salinity within the range of 0.1-0.25 mol/L for both salts with the amount of surface and IFT minimized at this point. In the other two salts, this point was delayed upon elevation of ionic strength and was observed at high salinity. In this case, divalent cations reduce tension rate compared to monovalent cations. Due to solubility of acidic and basic groups in water, pH of salt water illustrates an acidic trend. Results of the FTIR test confirmed solubility of these compounds as well. 相似文献
95.
We review theories of polyelectrolyte (PE) coacervation, which is the spontaneous association of oppositely charged units of PEs and phase separation into a polymer-dense phase in aqueous solution. The simplest theories can be divided into “physics-based” and “chemistry-based” approaches. In the former, PEs are treated as charged, long-chain, molecules, defined by charge level, chain length, and chain flexibility, but otherwise lacking chemical identity, with electrostatic interactions driving coacervation. The “chemistry-based” approaches focus on the local interactions between the species for which chemical identity is critical, and describe coacervation as the result of competitive local binding interactions of monomers and salts. In this article, we show how these approaches complement each other by presenting recent approaches that take both physical and chemical effects into account. Finally, we suggest future directions toward producing theories that are made quantitatively predictive by accounting for both long range electrostatic and local chemically specific interactions. 相似文献
96.
Na-Hyun Lee Sumin You Ali Taghizadeh Mohsen Taghizadeh Hye Sung Kim 《International journal of molecular sciences》2022,23(4)
Cell membrane cloaking technique is bioinspired nanotechnology that takes advantage of naturally derived design cues for surface modification of nanoparticles. Unlike modification with synthetic materials, cell membranes can replicate complex physicochemical properties and biomimetic functions of the parent cell source. This technique indeed has the potential to greatly augment existing nanotherapeutic platforms. Here, we provide a comprehensive overview of engineered cell membrane-based nanotherapeutics for targeted drug delivery and biomedical applications and discuss the challenges and opportunities of cell membrane cloaking techniques for clinical translation. 相似文献
97.
Ultrathin buffer layer at organic/organic interface for managing the recombination profile in organic light‐emitting diodes: Metal versus dielectric buffer 下载免费PDF全文
Davood Kalhor Ezeddin Mohajerani Omid HashemiPour Akram SalehiKian Mohsen Shojaeifar Mohammad Rasoul Babaei 《应用聚合物科学杂志》2016,133(36)
We report on the utilization of an ultrathin buffer layer at the organic/organic (O/O) interface to enhance device efficiency in organic light‐emitting diodes. Two different kinds of buffer layers are examined: metal and dielectric. It is shown that employment of an ultrathin Ag layer with a thickness of 1–2 nm enhances the device performance, while a MgF2 dielectric buffer cannot affect the device properties considerably. In particular, the turn‐on voltage of the device with an appropriate buffer layer is reduced about 3 V, its current efficiency increases by a factor of more than three, and the power efficiency increases by a factor of more than five in comparison to the control device when a Ag buffer layer is introduced at the O/O interface. By employment of the buffer layer at the interface, an accumulation of current carriers appears within the device that redistribute the recombination profile toward the interior part of the emissive layer. Also, morphological examinations reveal that distinguishable phase segregation occurs in the blend of the hole‐transport layer. In particular, the polymer component remains at the surface and facilitates the hole transport into the successive layers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43894. 相似文献
98.
Ali Mazahery Mohsen Ostad Shabani 《JOM Journal of the Minerals, Metals and Materials Society》2012,64(2):323-329
Commercial casting Al-Si (A356)-based composites reinforced with different volume fractions of alumina (Al2O3) nanoparticulates (average particle size 50 nm) were synthesized in this study. Particle distribution, hardness, and tensile properties in the as-cast condition were experimentally investigated. The A356 alloy composite showed an increase in hardness, elastic modulus, and tensile strength compared with monolithic alloys. Finally, a combination of an artificial neural network and the finite element method (FEM) was implemented to predict the microstructure and mechanical properties including grain size, length of silicon rods, amount of porosity, hardness, tensile yield stress, ultimate tensile stress, and elongation percentage. 相似文献
99.
A phase-field model is developed and used to simulate high-temperature synthesis of intermetallic compounds. The model is based on a thermodynamic formulation, which incorporates the formation of chemically ordered phases and the associated heat generation. In contrast to previous approaches to modelling of high-temperature synthesis of intermetallics, the present model can be used to analyse the kinetics of the process at the microstructure level. The model takes general thermodynamic and kinetic parameters as input and gives as output a spatially resolved sequence of phase formation, from which the overall reaction kinetics can be inferred. Thus, no additional assumption has to be made on the nature of the kinetic mechanisms or on the magnitude of the overall reaction rate. Beside prediction of the microstructure, the model captures the key thermal characteristics of the combustion synthesis in both modes of thermal explosion and self-propagation. The results of simulations, as applied to the case of intermetallic formation in a simplified Ni–Al system, are shown to be consistent with the existing experimental data. 相似文献
100.
Mohsen Nikpour Masoud Mirzaei Ya-Guang Chen Amir Aghaei Kaju Mehdi Bakavoli 《Inorganic chemistry communications》2009,12(9):m301-882
A new soluble organic–inorganic hybrid based on polyoxomolybdate, [C6H12N5O]3[(PO4)Mo12O36]·6H2O (1), has been successfully synthesized and characterized by using elemental analysis, IR, UV spectroscopies, 1H NMR technique, and single-crystal X-ray diffraction. According to the results of X-ray crystallography the anion [(PO4)Mo12O36]3− has a typical Keggin structure and the Mo–O distances of Mo–O–Mo bonds are alternately short and long in the polyoxoanion structure. Hirshfeld surface analyses, especially dnorm surface and fingerprint plots, are used for decoding intermolecular interactions in the crystal network and contribution of component units for the construction of the 3D architecture. The results indicate that in 1 the hydrogen bond interaction play a main role in the construction of the 3D architecture, especially the CHO interaction which overruns the classic NHO, NHO hydrogen bond interactions; van der Waals force between the peripheral atoms of component units cannot be ignored. 相似文献