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991.
Smaail Radi Ahmed Attayibat Abdelkrim Ramdani Maryse Bacquet 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):232-241
The immobilization of a thiophene-based tripodal ligand, with a donor sulfur, on the surface of an epoxide group containing a silica gel phase for the synthesis of a newly functionalized material based on porous silica-bound bi-thiophene tripodal ligand (SGBT) is described. The modified silica surface was characterized by 13C NMR of a solid sample, elemental analysis, and infrared spectra. This new material was also studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and BJH pore sizes, respectively. The target material exhibits good thermal stability as determined by thermogravimetry curves. The synthesized material was utilized in column and batch methods for adsorption of Hg2+, Cd2+, Pb2+, Cu2+, Zn2+, K+, Na+, and Li+, and the material exhibits an affinity only towards toxic heavy metals. 相似文献
992.
993.
S. Thongsang 《Journal of Macromolecular Science: Physics》2013,52(4):825-840
This article investigated the elastic response of natural rubber (NR) compounds filled with silica from fly ash particles (FASi) and commercial precipitated silica (PSi), through a dynamic rebound test. The effects of silica content and initial drop‐height on the height and number of rebounds, dynamic stiffness, and the energy loss were of interest. The results suggested that the unfilled NR vulcanizates exhibited a greater elastic response than the FASi and PSi‐filled vulcanized composites. For given silica contents, the NR compounds with FASi had better elastic response than those with PSi, where the elastic response decreased with an increase in silica content. The greater the silica contents, the higher the dynamic stiffness of the composites. The initial drop‐height had no effects on the elastic response change for the unfilled NR compound, but resulted in an increase in the energy loss for the silica‐filled NR composites. The differences in the elastic responses for the NR compounds filled with silica from FASi and PSi were associated with the differences in crosslink density and the filler–filler interaction influenced by content of bis(3‐triethoxysilylpropyl) tetrasulfane (designated as Si69) used. 相似文献
994.
A novel set of light-responsive polyelectrolytes has been developed and studied, to control and tune surface wettability by introducing various types of substituted R head-groups of azo polyelectrolytes in self-assembled multilayer (SAMU) films. As part of a larger project to develop polymer surfaces where one can exert precise control over properties important to proteins and cells in contact, photo-reversibly, we describe here how one can tune quite reliably the contact angle of a biocompatible SAMU, containing a photo-reversible azo chromophore for eventual directed cell growth. The azo polyelectrolytes described here have different substituted R head-group pairs of shorter-ionized hydrophilic COOH and SO3H, shorter non-ionized hydrophobic H and OC2H5, and larger non-ionized hydrophobic octyl C8H17 and C8F17, and were employed as polyanions to fabricate the SAMU onto silicon substrates by using the counter-charge polycation PDAC. The prepared SAMU films were primarily characterized by measurement of their contact angles with water. The surface wetting properties of the thin films were found to be dependent on the type of substituted R-groups of the azo polyelectrolytes through their degree of ionization, size, hydrophobicity/hydrophilicity, solubility, conformation, and inter-polymeric association and intra-polymeric aggregation. All these factors appeared to be inter-related, and influenced variations in hydrophobic/hydrophilic character to different extents of aggregates/non-aggregates in solution because of solvation effects of the azo polyanions, and were thus manifested when adsorbed as thin films via the SAMU deposition process. For example, one interesting observation is significantly higher contact angles of 79° for SAMU films of larger octyl R groups of PAPEA-C8F17 and PAPEA-C8H17 than for others with contact angles of 64° observed for non-polar R-groups of OC2H5 and H. Furthermore, lower contact angle values of 59° for SAMU films with polar R-groups of COOH and SO3H relative to that of non-polar R-groups are in accordance with their expected order of the hydrophilicity or hydrophobicity. It is possible that the large octyl groups are more effective in shielding the ionic functional groups on the substrate surface, and contributed less to the water drop-molecule interactions with ionic groups of the PDAC and/or AA groups. In addition, higher hydrophobicity of the SAMU films may be due to the incorporation of bulky and hydrophobic groups in these polyelectrolytes, which can produce aggregates on the surfaces of the SAMU films. Through understanding and controlling the complex aggregation behavior of the different substituted R-groups of these azo polyelectrolytes, and hence their adsorption on substrates, it appears possible to finely tune the surface energy of these biocompatible films over a wide range, enhance the photo-switching capabilities of the SAMU films, and tailor other surface properties for the development and application of new devices in diverse areas of microfluidics, specialty coatings, sensors, and biomedical sciences. 相似文献
995.
AbstractThe acrylamide copolymer with acrylamide as its main monomer is a modified polyacrylamide. In addition, the acrylamide copolymer is generally to dissolve or swell in water and can be used as thickener, dispersant, flocculant and so on. Therefore, using Acrylamide AM, 2-acrylamide-2-methyl propanesulfonic acid AMPS, dimethyldodecyl (2-acrylamidoethyl) ammoniumbromide AQ12 and vinyltriethoxysilane VTEO as raw materials so that a series of four-membered acrylamide copolymers are prepared in aqueous solution polymerization. The amphoteric structure in the polymer has a unique anti-polyelectrolyte behavior when it is electrically neutral, which can significantly improve the salt resistance of the aqueous polymer. In addition, the hydrolysis of the vinyltriethoxysilane containing silicon structure by hydrophobic association can improve the temperature resistance of the polymer. The optimal reaction conditions were determined by orthogonal experiment: the reaction temperature was 10?°C; the initiator concentration was 0.05?mol%; the monomer concentration was 25?wt% and the pH was 7. Properties of polymer solution indicated that the series of tetra-copolymer possessed salt-tolerant and heat-resisting performances. As an oil displacing agent, it can significantly improve the efficiency of oil displacement, and particularly highlights the effect of 4-member copolymer as an oil displacing agent. 相似文献
996.
Ângelo M.L. Denadai André M. de Oliveira Izabela M.P. Daniel Luan A. Carneiro Kherolayne C. Ribeiro Heloísa de O. Beraldo 《Supramolecular chemistry》2013,25(3):204-212
Chlorhexidine is a widely used, di-cationic, broad-spectrum antimicrobial agent and losartan is a well-known, anionic-specific antagonist of AT1 renin–angiotensin receptor that acts as an anti-hypertensive agent. The combination of these molecules gives a chlorhexidine di-losartanate (ClxLos2) hydrophobic ion pair that spontaneously aggregates into nanoparticles (NPs). This work investigated the formation of ClxLos2 NPs using the analysis of the solid state by fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy and in aqueous environment by calorimetric, zeta potential and dynamic light scattering titrations. Furthermore, to demonstrate the potential antimicrobial activity of ClxLos2, in vitro antibacterial tests were conducted against Staphylococcus aureus (ATCC 27664), Streptococcus viridans (ATCC 11563) and Enterococcus faecalis (ATCC 14508). Based on these studies, it is proposed that ClxLos2 could be used for controlled drug release based on ionic dissociation during dilution, thereby avoiding the use of any solid matrix. 相似文献
997.
Laurens van Gelderen Gadi Rothenberg V. Roberto Calderone Karen Wilson N. Raveendran Shiju 《应用有机金属化学》2013,27(1):23-27
Copper immobilized on a functionalized silica support is a good catalyst for the homocoupling of terminal alkynes. The so‐called Glaser–Hay coupling reaction can be run in air with catalytic amounts of base. The copper catalyst is active for multiple substituted alkynes, in both polar and non‐polar solvents, with good to excellent yields (75–95%). Depending on the alkyne, full conversion can be achieved within 3–24 h. The catalyst was characterized by TGA, inductively coupled plasma and X‐ray photoelectron spectroscopy. Leaching tests confirm that the catalyst is and remains heterogeneous. Importantly, the overall reaction requires only alkyne and oxygen (in this case, air) as reagents, making this a clean catalytic oxidative coupling reaction. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
998.
An improved and eco‐friendly procedure has been developed to generate mesoporous silica‐supported palladium nanoparticles (SiO2@PdNP) that could be used as a sustainable heterogeneous Pd catalyst for phosphine‐free Suzuki–Miyaura and Heck coupling reactions with excellent turnover number and turnover frequency. The presence of Pd on the silica surface was detected by X‐ray diffraction and the structural morphology of SiO2@PdNP was obtained by transmission electron microscopy. The heterogeneous catalytic system is recyclable and leaching of the metal after the reaction is not apparently observed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
Silica obtained by acid treatment of sepiolite was used as a support for catalysts consisting of palladium complexes of 2‐ and 3‐thiophenecarbaldehyde. The support and the catalysts were characterized by X‐ray diffraction, and solid‐state 29Si and 13C nuclear magnetic resonance spectroscopies. The supported palladium catalysts were used in the Suzuki reaction of bromobenzene with phenylboronic acid. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
1000.
M. Emin Çorman Nilay Bereli Serpil Özkara Lokman Uzun Adil Denizli 《Biomedical chromatography : BMC》2013,27(11):1524-1531
As alternative hydrophobic adsorbent for DNA adsorption, supermacroporous cryogel disks were synthesized via free radical polymerization. In this study, we have prepared two kinds of cryogel disks: (i) poly(2‐hydroxyethyl methacrylate‐N‐methacryloyl‐l ‐tryptophan) [p(HEMA‐MATrp)] cryogel containing specific hydrophobic ligand MATrp; and (ii) monosize p(HEMA‐MATrp) particles synthesized via suspension polymerization embedded into p(HEMA) cryogel structure to obtain p(HEMA‐MATrp)/p(HEMA) composite cryogel disks. These cryogel disks containing hydrophobic functional group were characterized via swelling studies, Fourier transform infrared spectroscopy, elemental analysis, surface area measurements and scanning electron microscopy. DNA adsorption onto both p(HEMA‐MATrp) cryogel and p(HEMA‐MATrp)/p(HEMA) composite cryogels was investigated. Maximum adsorption of DNA on p(HEMA‐MATrp) cryogel was found to be 15 mg/g polymer. Otherwise, p(HEMA‐MATrp)/p(HEMA) composite cryogels significantly increased the DNA adsorption capacity to 38 mg/g polymer. Composite cryogels could be used repeatedly without significant loss on adsorption capacity after 10 repetitive adsorption–desorption cycles. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献