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Various Organic Solvents (various + organic_solvent)
Selected AbstractsSolvent-Resistant PDMS Microfluidic Devices with Hybrid Inorganic/Organic Polymer CoatingsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Bo-Yeol Kim Abstract This study presents a method for the fabrication of solvent-resistant poly(dimethylsiloxane) (PDMS) microfluidic devices by coating the microfluidic channel with a hybrid inorganic/organic polymer (HR4). This modification dramatically increases the resistance of PDMS microfluidic channels to various solvents, because it leads to a significant reduction in the rate of solvent absorption and consequent swelling. The compatibility of modified PDMS with a wide range of solvents is investigated by evaluating the swelling ratio measured through weight changes in a standard block. The HR4-modified PDMS microfluidic device can be applied to the formation of water-in-oil (W/O) and oil-in-water (O/W) emulsions. The generation of organic solvent droplets with high monodispersity in the microfluidic device without swelling problems is demonstrated. The advantage of this proposed method is that it can be used to rapidly fabricate microfluidic devices using the bulk properties of PDMS, while also increasing their resistance to various organic solvents. This high compatibility with a variety of solvents of HR4-modified PDMS can expand the application of microfluidic systems to many research fields. [source] Molecular Design of Superabsorbent Polymers for Organic Solvents by Crosslinked Lipophilic Polyelectrolytes,ADVANCED FUNCTIONAL MATERIALS, Issue 24 2008Toshikazu Ono Abstract Molecular design of lipophilic polyelectrolyte gels as superabsorbent polymers that exhibit a high degree of swelling in less-polar and nonpolar organic solvents is demonstrated. A small amount of tetraalkylammonium tetraphenylborate with long alkyl chains as a lipopholic ion pair is incorporated into crosslinked polyacrylates with variable alkyl chain lengths to provide novel lipophilic polyelectrolyte gels. Their swelling degree becomes more than 100 times as much as their dried weights in various organic solvents. The high effectiveness of the swellable solvents shifts to the polar ones by decreasing the length of the alkyl chain. Swelling or collapsing of the lipophilic polyelectrolyte gels originates from both incompatibility of the polymer chains in the media and dissociation of ionic groups. Thus, a unique superabsorbency is observed when the polymer chains have good compatibility with the solvents and the solvents have relatively high polarities enough to dissociate the ionic groups. By varying the polarity of the neutral monomer in these polyelectrolyte gels, the design of gels that can absorb solvents of nearly any polarity is demonstrated. [source] Irradiation synthesis of biopolymer-based superabsorbent hydrogel: Optimization using the Taguchi method and investigation of its swelling behaviorADVANCES IN POLYMER TECHNOLOGY, Issue 2 2009Ghasem R. Bardajee Abstract In this report, the synthesis of a novel superabsorbent hydrogel via ,-irradiation graft copolymerization of acrylamide onto sodium alginate and kappa-carrageenan hybrid backbones in a homogeneous solution is described. The Taguchi method was used as a powerful experimental design tool for synthesis optimization. A series of superabsorbent hydrogels was synthesized by proposed conditions of Qualitek-4 software. Considering the results of nine trials according to analysis of variance, optimum conditions were proposed. The swelling behavior of optimum superabsorbent hydrogels was studied in various solutions, with pH values ranging from 1 to 13. In addition, swelling kinetics, swelling in various organic solvents, the absorbency under load, and on,off switching behavior were investigated. Also, hydrogel formation was confirmed by Fourier transform infrared spectroscopy. Surface morphology of the synthesized hydrogels was assessed by scanning electron microscopy. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:131,140, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20154 [source] Thermodynamic activity-based enzyme kinetics: Efficient tool for nonaqueous enzymologyAICHE JOURNAL, Issue 3 2001Georgina C. Sandoval Lipase-catalyzed synthesis reactions must be performed in nonaqueous media (organic solvents or solvent-free systems). The choice of the optimal solvent is usually a fastidious task that necessitates the determination of kinetic parameters in each solvent. The approach used here, to overcome the lack of a model that can predict the kinetics whatever the solvent, consists in the use of thermodynamic activities instead of concentrations of components, and assumes that activity-based kinetic parameters are the same in all solvents. This assumption is discussed, and a solution is proposed which takes into account some observed residual solvent effects. The reaction chosen to test this approach was the esterification of oleic acid with ethanol catalyzed by an immobilized lipase, Lipozyme. For this reaction, the kinetics predicted in various organic solvents and in solvent-free systems is in agreement with the experimental data. [source] 2-Ethylhexyl-2,4,5-trimethoxycinnamate and di-(2-ethylhexyl)-2,4,5-trimethoxybenzalmalonate as novel UVA filtersJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2007Thitinun Monhaphol A series of 2-ethylhexylmethoxy substituted cinnamates and benzalmalonates have been synthesized and characterized. 2-Ethylhexyl-2,4,5-trimethoxycinnamate (E8) and di-(2-ethylhexyl)-2,4,5-trimethoxybenzalmalonate (B8) show UVA absorption with high molar absorption coefficients (12000-14000 cm,1 M,1 at 350 nm). E8 undergoes trans to cis photoisomerization under UVA exposure causing the decrease in UV absorption efficiency. E8 is more photostable than butyl methoxydibenzoylmethane (BMDBM). For example, 41.64 J cm,2 UVA irradiation produces 20 ± 2% and 25 ± 2% loss in UV absorption for E8 and BMDBM, respectively. Similar irradiation produces no change in the UV absorption of B8. Both the oily liquid E8 and the yellow solid B8 can be dissolved in various organic solvents, ranging from methanol to hexane, various silicone fluids and 2-ethylhexyl-4-trimethoxycinnamate (EHMC, a widely used UVB filter). A liquid broadband filter comprising B8 and EHMC shows excellent photostability in both UVB and UVA regions. [source] The influence of organic solvent and ionic liquids on the selective formation of 2-(2-ethylhexyl)-3-phenyl-1,2-oxaziridine mediated by lipases,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2010Thiago Bergler Bitencourt Abstract This paper describes the influence of the addition of ionic liquids (ILs) based on [BMIm][X], where [X],=,SCN, Cl, BF4, and PF6, on the chemo-enzymatic oxidation of N -benzyliden-2-ethylhexylamine to form the corresponding E- and Z -isomers of oxaziridines mediated by Pseudomonas sp. (PSL) and Candida antarctica (CAL-B) lipases in various organic solvents at room temperature (25,°C) with urea hydrogen peroxide (UHP). The results showed that the use of different organic solvents in the presence of ILs, critically changes the conversions (5,99%) and the isomeric ratio E:Z, (50,100% E -isomer) of the products formed. Copyright © 2010 John Wiley & Sons, Ltd. [source] Synthesis, photoluminescence, and electrochromic properties of wholly aromatic polyamides bearing naphthylamine chromophoresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2006Guey-Sheng Liou Abstract A series of novel polyamides with pendent naphthylamine units having inherent viscosities of 0.15,1.02 dL/g were prepared via direct phosphorylation polycondensation from various diamines and a naphthylamine-based aromatic dicarboxylic acid, 1-[N,N -di(4-carboxyphenyl)amino]naphthalene. These amorphous polyamides were readily soluble in various organic solvents and could be cast into transparent and tough films. The aromatic polyamides had useful levels of thermal stability associated with high glass-transition temperatures (268,355 °C), 10% weight loss temperatures in excess of 480 °C, and char yields at 800 °C in nitrogen higher than 60%. These polymers showed maximum ultraviolet,visible absorption at 350,358 nm and exhibited fluorescence emission maxima around 435,458 nm in N -methyl-2-pyrrolidinone solutions with fluorescence quantum yields ranging from 0.4 to 15.0%. The hole-transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple around 1.08,1.16 V (oxidation onset potential) versus Ag/AgCl in an acetonitrile solution and revealed good stability of the electrochromic characteristics, with a color change from colorless to green at applied potentials ranging from 0 to 1.6 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6094,6102, 2006 [source] Spectroscopic studies of charge transfer complexes of meso -tetra- p -tolylporphyrin and its zinc complex with some aromatic nitro acceptors in different organic solventsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2007Mohamed E. El-Zaria Abstract The charge transfer complex (CTC) formation of 5,10,15,20-tetra(p -tolyl)porphyrin (TTP) and zinc 5,10,15,20-tetra(p -tolyl)porphyrin with some aromatic nitro acceptors such as 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, 3,5-dinitrobenzoic acid (DNB) and 2,4-dinitrophenol (DNP) was studied spectrophotometrically in different organic solvents at different temperatures. The spectrophotometric titration, Job's and straight line methods indicated the formation of 1:1 CTCs. The values of the equilibrium constant (KCT) and molar extinction coefficient (,CT) were calculated for each complex. The ionization potential of the donors and the dissociation energy of the charge transfer excited state for the CTC in different solvents was also determined and was found to be constant. The spectroscopic and thermodynamic properties were observed to be sensitive to the electron affinity of the acceptors and the nature of the solvent. No CT band was observed between Zn-TTP as donor and DNP or DNB as acceptors in various organic solvents at different temperature. Bimolecular reactions between singlet excited TTP (1TTP*) and the acceptors were investigated in solvents with various polarities. A new emission band was observed. The fluorescence intensity of the donor band decreased with increasing the concentration of the acceptor accompanied by an increase in the intensity of the new emission. The new emission of the CTCs can be interpreted as a CT excited complex (exciplex). Copyright © 2007 John Wiley & Sons, Ltd. [source] Highly Fluorescent Lyotropic Mesophases and Organogels Based on J-Aggregates of Core-Twisted Perylene Bisimide DyesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2008Xue-Qing Li A new perylene bisimide dye has been synthesized that forms highly fluorescent J-aggregates in various organic solvents and its gelation in polar solvents like acetone and dioxane is observed (see figure), whilst anisotropic highly viscous lyotropic mesophases are created in apolar solvents such as n -hexane or methylcyclohexane. [source] Aldol reaction catalyzed by a hydrophilic catalyst in aqueous micelle as an enzyme mimic systemCHIRALITY, Issue 5 2009Hefeng Zhang Abstract Chitosan-supported L -proline complex was synthesized and applied as a catalyst for the direct asymmetric aldol reaction in various organic solvents and water as well. It was found that the novel synthesized catalyst was able to efficiently catalyze the aldol reaction in various media. The catalytic capacity and stereoselectivity of the catalyst were obviously improved with the introduction of aqueous micelle, possibly because the micelle functioned as a hydrophobic pocket, like the hydrophobic portion in enzymes. Moreover, the present synthetic catalyst showed performance similar to that of enzymes and could be used as a model of enzyme catalysis to help better understand the mystic mechanism of enzymes. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||