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排序方式: 共有209条查询结果,搜索用时 19 毫秒
21.
Anjan Biswas Abhijit Bandyopadhyay Nikhil K. Singha Anil K. Bhowmick 《Journal of polymer science. Part A, Polymer chemistry》2008,46(24):8023-8040
Direct sulfonation and styrene‐mediated sulfonation were carried out onto metallocene‐based poly(ethylene‐co‐octene) (POE) and poly(ethylene‐co‐butene) (PBE) elastomers to impart polarity on the completely nonpolar rubbery matrices and to prepare a new class of elastomer. The influence of styrene‐grafting and pendant chain length on the degree of sulfonation was also studied. The effects of sulfonation, styrene grafting and styrene‐mediated sulfonation at their optimized levels on various physicomechanical properties were thoroughly investigated, and the resultant properties were correlated with structures of the modified elastomers. Higher extent of sulfonic acid groups were introduced through direct sulfonation in comparison with the styrene‐mediated sulfonation, whereas better thermal and mechanical properties were obtained through styrene‐mediated sulfonation in comparison with the direct sulfonation process. PBE had shown higher degree of sulfonation and percentage grafting than POE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8023–8040, 2008 相似文献
22.
We have developed simple, greener, safer multicomponent synthesis series of 4-arylidene-2-phenyl-5(4H) oxazolones 4(a-r) catalyzed by Bronsted acid ionic liquid as triethylammonium hydrogen sulfate [Et3NH][HSO4] and catalytic amount of acetic anhydride and sodium acetate with excellent yields (90–99%). The protocol offers economical, environmentally benign, solvent-free conditions, and recycle–reuse of the catalyst and easily available starting as benzoyl chloride 1, amino acid 2 and a variety of aldehydes 3. The cyclization followed by condensation of benzoyl chloride, amino acid, and a variety of aldehydes catalyzed by ILs [Et3NH][HSO4] and catalytic amount of acetic anhydride and sodium acetate. The final products were confirmed by their characterization data such as FTIR, 1H-NMR, 13C-NMR, Mass, high-resolution mass spectra and were compared with its reported method. 相似文献
23.
Nesreen Alzoghoul Alsmadi Aniket S. Wadajkar Weina Cui Kytai T. Nguyen 《Journal of nanoparticle research》2011,13(12):7177-7186
The objective of this research was to compare the effects of two different surfactants on the physicochemical properties of
thermo-responsive poly(N-isopropylacrylamide-acrylamide-allylamine) (PNIPAAm-AAm-AH)-coated magnetic nanoparticles (MNPs). Sodium dodecyl sulfate
(SDS) as a commonly used surfactant in nanoparticle formulation process and Pluronic F127 as an FDA approved material were
used as surfactants to synthesize PNIPAAm-AAm-AH-coated MNPs (PMNPs). The properties of PMNPs synthesized using SDS (PMNPs-SDS)
and PF127 (PMNPs-PF127) were compared in terms of size, polydispersity, surface charge, drug loading efficiency, drug release
profile, biocompatibility, cellular uptake, and ligand conjugation efficiency. These nanoparticles had a stable core–shell
structure with about a 100-nm diameter and were superparamagnetic in behavior with no difference in the magnetic properties
in both types of nanoparticles. In vitro cell studies showed that PMNPs-PF127 were more cytocompatible and taken up more by
prostate cancer cells than that of PMNPs-SDS. Cells internalized with these nanoparticles generated a dark negative contrast
in agarose phantoms for magnetic resonance imaging. Furthermore, a higher doxorubicin release at 40 °C was observed from PMNPs-PF127,
and the released drugs were pharmacologically active in killing cancer cells. Finally, surfactant type did not affect the
conjugation efficiency to the nanoparticles when folic acid was used as a targeting ligand model. These results indicate that
PF127 might be a better surfactant to form polymer-coated magnetic nanoparticles for targeted and controlled drug delivery. 相似文献
24.
S. M. Islam Sanchita Mondal Anupam Singha Roy Paramita Mondal Manir Mobarak Dildar Hossain Palash Pandit 《Transition Metal Chemistry》2010,35(3):305-313
A polymer-anchored Pd(II) Schiff base complex has been synthesized by reacting a polymeric amine with 2-pyridinecarboxaldehyde
to get the polymer-anchored Schiff base, which was then reacted with palladium acetate. The catalyst was characterized by
physicochemical and spectroscopic methods. It shows excellent catalytic activity in the Sonogashira coupling of phenylacetylene
with aryl halides using triethylamine as a base and copper iodide as a co-catalyst in water under open air at 70 °C. We have
also studied the effects of base and solvent on the coupling reaction. Sonogashira reactions of phenylacetylene with a variety
of functionalized aryl halides were performed under the optimized reaction conditions. This catalyst gives excellent yields
without the use of phosphine ligands. Further experiments showed that the catalyst can be used five times without much loss
in the catalytic activity. 相似文献
25.
Manirul Islam Paramita Mondal Anupam Singha Roy Kazi Tuhina 《Transition Metal Chemistry》2010,35(4):427-435
A poly(3,6-dibenzaldimino N-vinyl carbazole) Pd(II) complex has been synthesized and characterized by physicochemical and spectroscopic techniques. The complex was found to be highly active toward hydrogenation reactions of various organic substrates under atmospheric pressure at ambient temperature. A tentative reaction mechanism is proposed on the basis of kinetic studies and isolation of reactive intermediates. The catalyst shows good conversion rates, thermal stability and recyclability. 相似文献
26.
Dhruba J. Haloi Santanu Roy Nikhil K. Singha 《Journal of polymer science. Part A, Polymer chemistry》2009,47(23):6526-6533
This investigation reports the atom transfer radical copolymerization (ATRcP) of glycidyl methacrylate (GMA) and 2‐ethylhexyl acrylate (EHA). Poly(glycidyl methacrylate) (PGMA) has easily transformable pendant oxirane group and poly(2‐ethylhexyl acrylate) (PEHA) has very low Tg. They are the important components of coating and adhesive materials. Copolymerization of GMA and EHA was carried out in bulk and in toluene at 70 °C at different molar feed ratios using CuCl as catalyst in combination with 2,2′‐bypyridine (bpy) as well as N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) as ligand. The molecular weight (Mn) and the polydispersity index (PDI) of the polymers were determined by GPC analysis. The molar composition of the copolymers was determined by 1H NMR analysis. The reactivity ratios of GMA (r1) and EHA (r2) were determined using Finemann‐Ross and Kelen‐Tudos linearization methods and those had been compared with the literature values for conventional free radical copolymerization. The thermal properties of the copolymers were studied by DSC and TGA analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6526–6533, 2009 相似文献
27.
Here, the large amplitude free flexural vibration behaviors of thin laminated composite skew plates are investigated using finite element approach. The formulation includes the effects of shear deformation, in-plane and rotary inertia. The geometric non-linearity based on von Karman's assumptions is introduced. The non-linear governing equations obtained employing Lagrange's equations of motion are solved using the direct iteration technique. The variation of non-linear frequency ratios with amplitudes is brought out considering different parameters such as skew angle, number of layers, fiber orientation, boundary condition and aspect ratio. The influence of higher vibration modes on the non-linear dynamic behavior of laminated skew plates is also highlighted. The present study reveals the redistribution of vibrating mode shape at certain amplitude of vibration depending on geometric and lamination parameters of the plate. Also, the degree of hardening behavior increases with the skew angle and its rate of change depends on the level of amplitude of vibration. 相似文献
28.
Manirul?IslamEmail author Dildar?Hossain Paramita?Mondal Kazi?Tuhina Anupam?Singha?Roy Sanchita?Mondal Manir?Mobarak 《Transition Metal Chemistry》2011,36(2):223-230
A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical
and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates
including alkenes and alcohols using H2O2 as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate
to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between
the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out. 相似文献
29.
The flow field downstream of a bluff body in a typical open channel flow was explored by two-dimensional particle image velocimetry. Measurements are obtained in horizontal planes at the near-bed, mid-depth and near-surface locations downstream of the body up to a streamwise distance of 10D, where D is the width of the body. The dimensionless streamwise defect velocity profile of the wake flow matches well with the data of a previous investigation and does not reflect any dependency on the distance from the bed. However, the nature of development of the recirculation region is found to be different at the three vertical locations. The time-averaged streamline pattern indicates the existence of a unique nodal pattern close to the bed. The variation of the half-width is also found to be affected by the presence of the bed and the free surface. The bed friction arrests the transverse growth of the shear layer, and the free-surface helps to redistribute the turbulent kinetic energy in the streamwise and transverse directions. Swirling strength analysis is carried out to compare the behavior and statistics of the vortex population in the vertical direction. The prevailing magnitude of the swirling strength is found to be different at the three vertical locations. Bed friction assists to dissipate vorticity rapidly, and therefore reduces the probability of appearance of strong vortices close to the bed. 相似文献
30.
Chloroform-vapor annealing of thin films of propoxyethyl perylene tetracarboxylic diimide (PE-PTCDI, an n-type semiconductor) deposited on glass or mica leads to formation of well-defined one-dimensional self-assemblies (e.g. nanobelts), which show optically uniaxial properties as demonstrated by the linearly polarized emission. 相似文献