Showing papers on "Solvent published in 2004"
TL;DR: The extraordinary potential of ionic liquids in materials synthesis is described in this minireview and a physicochemical explanation is given.
Abstract: Ionic liquids are a new class of organic solvents with high polarity and a preorganized solvent structure. Very polar reactions can be carried out in these liquid in the absence of or with a controlled amount of water, and crystalline nanoparticles can be synthesized conveniently at ambient temperatures. The pronounced self-organization of the solvent is used in the synthesis of self-assembled, highly organized hybrid nanostructures with unparalleled quality. The extraordinary potential of ionic liquids in materials synthesis is described in this minireview and a physicochemical explanation is given.
1,118 citations
TL;DR: The catalytic properties of the metal-organic framework compound Cu 3 (BTC) 2 (H 2 O) 3 ǫ x H 2 O (BTC=benzene 1,3,5-tricarboxylate) were explored in this article.
981 citations
TL;DR: In this article, the authors investigated a range of solvents with higher boiling points and found that 1,2,4-trichlorobenzene with good solubility and a high boiling point significantly improves the field-effect mobilities up to 0.12 cm2/(V s) with on:off ratios of 106.
Abstract: Chloroform is a general solvent for poly(3-hexylthiophene) (P3HT) active layers in field-effect transistors. However, its low boiling point and rapid evaporation limit the time for crystallization during the spin-coating process, and field-effect mobilities achieved for P3HT films spin-coated from chloroform are typically on the order of 0.01 cm2/(V s). Here we investigate a range of solvents with higher boiling points. We find that 1,2,4-trichlorobenzene with good solubility and a high boiling point significantly improves the field-effect mobilities up to 0.12 cm2/(V s) with on:off ratios of 106. By controlling the microstructure through the choice of solvent while keeping the molecular weight fixed, we observe a clear correlation between the field-effect mobility and the degree of microcrystalline order as measured by X-ray diffraction, as well as the strength of polaronic relaxation of charge carriers in the accumulation layer as measured by optical spectroscopy of field-induced charge.
902 citations
TL;DR: This phase of emulsion optimisation represents an important step in the process of polymeric nanocapsules preparation using nanoprecipitation or interfacial polycondensation combined with spontaneous emulsification technique.
772 citations
TL;DR: In this article, a roadmap for the literature values of density, viscosity, melting and glass transition temperatures, thermal stability, empirical solvent parameters, absorption, toxicity, surface tension, heat capacity, and thermal conductivity is provided.
Abstract: Ionic liquids are good solvents for catalytic reactions. The rational selection of the appropriate ionic liquid solvent for a particular reaction requires general knowledge of the properties of ionic liquids, and the details of some properties of the specific ionic liquid solvents being considered. The solvent properties of ionic liquids that are relevant to catalysis are discussed, and sources of the values of those properties for ionic liquids are identified. A roadmap for the literature values of density, viscosity, melting and glass transition temperatures, thermal stability, empirical solvent parameters, absorption, toxicity, surface tension, heat capacity, and thermal conductivity is provided.
745 citations
TL;DR: In this paper, six solvents [acetic acid, acetonitrile, m-cresol, toluene, tetrahydrofuran (THF) and dimethylformamide (DMF)] with different properties (eg density, boiling point, solubility parameter, dipole moment and dielectric constant) were used to prepare electrospun polystyrene (PS) fibers.
Abstract: Six solvents [acetic acid, acetonitrile, m-cresol, toluene, tetrahydrofuran (THF) and dimethylformamide (DMF)] with different properties (eg density, boiling point, solubility parameter, dipole moment and dielectric constant) were used to prepare electrospun polystyrene (PS) fibers. Fiber diameters were found to decrease with increasing density and boiling point of the solvents. A large difference between the solubility parameters of PS and the solvent was responsible for the bead-on-string morphology observed. Productivity of the fibers (the numbers of fiber webs per unit area per unit time) increased with increasing dielectric constant and dipole moment of the solvents. Among the solvents studied, DMF was the best solvent that provided PS fibers with highest productivity and optimal morphological characteristics. The beadless, well-aligned PS fibers with a diameter of ca 0.7 µm were produced from the solution of 10 % (w/v) of PS in DMF at an applied electrostatic field of 15 kV/10 cm, a nitrogen flow rate of 101 ml min−1 and a rotational speed of the collector of 1500 rev min−1. Copyright © 2004 Society of Chemical Industry
425 citations
TL;DR: The authors showed that protein solubility will be markedly lower in polar solvents such as ethanol and that proteins will be essentially insoluble in cyclohexane, and even more stable in a vacuum.
Abstract: Proteins carry out the most difficult tasks in living cells. They do so by interacting specifically with other molecules. This requires that they fold to a unique, globular conformation that is only marginally more stable than the large ensemble of unfolded states. The folded state is stabilized mainly by the burial and tight packing of over 80% of the peptide groups and non-polar side chains. If life as we know it is to exist in a solvent other than water, the folded state must be stable and soluble in the new solvent. Our analysis suggests that proteins will be unstable in most polar solvents such as ethanol, extremely stable in non-polar solvents such as cyclohexane, and even more stable in a vacuum. Our solubility studies suggest that protein solubility will be markedly lower in polar solvents such as ethanol and that proteins will be essentially insoluble in non-polar solvents such as cyclohexane. For these and other reasons it seems unlikely that the life we know could exist in any solvent system other than water.
340 citations
TL;DR: This study investigates the mechanism of the solvent elimination from the emulsion droplets and its influence on the particle morphology, encapsulation and release behavior of microparticles in double emulsion formulations.
331 citations
TL;DR: In this study, eight solvent parameters, including hydrogen bond acceptor propensity, hydrogen bond donor propensity, polarity/dipolarity, dipole moment, dielectric constant, viscosity, surface tension and cohesive energy density, of 96 solvents were collected and separated into 15 solvent groups.
327 citations
TL;DR: In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported, and a reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.
Abstract: A novel and very mild method for the oxidation of primary alcohols to aldehydes with excellent conversions has been developed. The reaction is carried out under air at room temperature and is catalysed using a [copper(II)-(N ligand)n] complex with TEMPO and a base as co-catalysts. In this paper, the performance of a series of N-containing ligands, as well as different copper(II) salt precursors in different solvents are reported. Best results are obtained in acetonitrile/water as solvent using a copper(II) catalyst generated in situ from a Cu(II) salt with weak or non-coordinating anions and bipyridine ligands with electron-donating substituents. A reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.
311 citations
TL;DR: In particular, relatively polar solvents that are able to transport water through the emulsion continuous phase (Ostwald ripening) are shown to produce much lower surface areas than analogous resins prepared by homogeneous solution polymerization of divinylbenzene.
Abstract: Poly(divinylbenzene) emulsion-derived (PolyHIPE) solid foams prepared with porogens (toluene, chlorobenzene, (2-chloroethyl)benzene, 1,2-dichlorobenzene, and 1-chloro-3-phenylpropane) in the oil phase have morphologies and surface areas that are strongly influenced by the nature of the porogen. For the case where the surfactant employed is Span 80, we show that the solid foam structure depends on (i) the ability of the solvent to swell the growing network, (ii) the solvent polarity, and (iii) the ability of the solvent to adsorb at the emulsion interface. In particular, relatively polar solvents that are able to transport water through the emulsion continuous phase (Ostwald ripening) are shown to produce much lower surface areas than analogous resins prepared by homogeneous solution polymerization of divinylbenzene in the presence of the solvent in question alone. The influence of Ostwald ripening is further suggested by the observation that surface area decreases with increasing emulsion aqueous phase co...
TL;DR: In this paper, the effects of nature and composition of alcohol on the resultant CeO 2 nanoparticles were investigated by homogeneous precipitation in alcohol/water mixed solvents, and it was found that the resulting particles were primary particles confirmed by quite good consistency in the particle sizes from TEM, XRD and BET analyses.
TL;DR: In solvents with dielectric constants of 10 or less, ion association constants, K(A), are as much as 2 orders of magnitude lower with [B(C(6)F(5))(4)](-), TFAB, as the electrolyte anion and the degree of this lowering is related to the acceptor property of the solvent.
Abstract: Cyclic voltammetry experiments at minielectrodes exhibit less ohmic error for lower polarity solvents when the supporting electrolyte anion is [B(C6F5)4]- rather than one of the smaller traditional anions such as [BF4]-, [PF6]-, or [ClO4]-. Conductance measurements have been performed for [NBu4][B(C6F5)4] in tetrahydrofuran, dichloromethane, benzotrifluoride, and acetonitrile and compared with results for [NBu4]+ salts of several traditional anions in the same solvents. In solvents with dielectric constants of 10 or less, ion association constants, KA, are as much as 2 orders of magnitude lower with [B(C6F5)4]-, TFAB, as the electrolyte anion and the degree of this lowering is related to the acceptor property of the solvent. Analyses carried out on the basis of a Fuoss model attribute this fact to differences in concentrations of contact ion pairs rather than of solvent-separated ion pairs. The greater dissociation of the TFAB ion is attributed to its highly delocalized charge.
TL;DR: Toluene was demonstrated to be the best exchange solvent due to its miscibility with MeCN and stronger responses of relatively more polar pesticides as compared to hexane and isooctane; therefore solvent exchange is generally not required before GC analysis.
TL;DR: In this article, the authors examined whether imidazolium-based ionic liquids can replace conventional organic solvents in the extractive fermentation of lactate by investigating their extraction behaviors and solvent toxicity.
TL;DR: In this article, a review of the solvatochromic properties of new hydrophilic and lipophilic betaine dyes with better solubility in water (respectively, nonpolar solvents) is described.
Abstract: Solutions of the zwitterionic betaine dye 4-(2,4,6-triphenylpyridinium-1-yl)-2,6-di- phenylphenolate are solvatochromic, thermochromic, piezochromic, and halochromic. That means the position of its longest-wavelength intramolecular charge-transfer absorption band depends on solvent polarity, solution temperature, external pressure, and the nature and con- centration of added salts. The extraordinarily large negative solvatochromism of this standard betaine dye has been used to establish UV/vis spectroscopically an empirical scale of solvent polarity, called E T (30), respectively E T scale, meanwhile known for many organic solvents and solvent mixtures. In this review, the solvatochromic properties of some new hydrophilic and lipophilic betaine dyes with better solubility in water (respectively, nonpolar solvents), as well as some recent applications of these betaine dyes in various fields of interest (e.g., microheterogeneous (micellar) and polymer solutions, chemical sensors, as well as surface polarity of silicas, aluminas, and cellulose derivatives) are described.
TL;DR: Results from molecular dynamics simulations of surfactant-solubilized subtilisin BPN' in three organic solvents (octane, tetrahydrofuran, and acetonitrile) and in pure water indicate that the behavior of hydration water on the enzyme surface and in the active site is an important determinant of biological function especially in low water media.
TL;DR: In this article, the authors describe the oxidation of several model S-containing molecules with hydrogen peroxide in a two liquid-liquid (L-L) phase system with a phase transfer catalyst under atmospheric pressure in the 333-353 K temperature range.
TL;DR: It was shown that all of the amines are more nucleophilic in the ionic liquids than in the molecular solvents studied in this work, and can be explained in part by the differing hydrogen-bonding properties, as shown by the Kamlet-Taft solvent parameters and the formation of hydrogen bonds between the solvent and the nucleophiles.
Abstract: In this work we report the effect of ionic liquids on a class of charge-neutral nucleophiles. We have studied the reactions of nbutylamine, di-nbutylamine, and tri-nbutylamine with methyl p-nitrobenzenesulfonate in [bmpy][N(Tf)2], [bmpy][OTf], and [bmim][OTf] (bmpy = 1-butyl-1-methylpyrrolidinium; bmim = 1-butyl-3-methylimidazolium) and compared their reactivities, k2, to those for the same reactions in the molecular solvents dichloromethane and acetonitrile. It was shown that all of the amines are more nucleophilic in the ionic liquids than in the molecular solvents studied in this work. Comparison is also made with the effect of ionic liquids on the reactivity of chloride ions, which are deactivated in ionic liquids. The Eyring activation parameters revealed that changes in the activation entropies are largely responsible for the effects seen. This can be explained in part by the differing hydrogen-bonding properties, as shown by the Kamlet−Taft solvent parameters, of each of these solvents and the form...
TL;DR: In this paper, a new rational method of synthesis of nanocrystalline iron (II, III) oxide is based on the elevated-temperature hydrolysis of chelate iron alkoxide complexes in solutions of corresponding alcohol, diethylene glycol, and N-methyl diethanolamine.
Abstract: A new rational method of synthesis of nanocrystalline iron (II, III) oxide is based on the elevated-temperature hydrolysis of chelate iron alkoxide complexes in solutions of corresponding alcohol, diethylene glycol, and N-methyl diethanolamine. The rates of reaction and crystallization are easily tuned by varying the concentration of reactants and changing the temperature. The size of the nanocrystals is controlled by changing the complexing strength of the reaction medium: 5.7 nm in diethylene glycol, 16.8 nm in N-methyl diethanolamine, and 12.7 nm in a 1:1 mixture of both solvents. The nanocrystalline powdered Fe3O4 products were isolated with a high yield. The surface of the obtained nanocrystals is passivated by molecules of adsorbed donating solvent that provide stability against agglomeration, provide solubility in polar protic solvents (water and methanol), and allow reactions at the nanocrystal surface.
TL;DR: Of all the surfaces examined in this study, the cells favoured the SG aspect of ethyl acetate cast PCL films, the surface of which had the finest pore size and relatively low contact angle.
TL;DR: The results show that block copolymers with shorter hydrophilic blocks assemble into larger vesicles, whereas the effect of acrylic acid block length occurs because of the relationship among the block length, the width of the molecular weight distribution, and the stabilization of the vesicle curvature.
Abstract: Polymeric vesicles have attracted considerable attention in recent years, since they are a model for biological membranes and have versatile structures with several practical applications. In this study, we prepare vesicles from polystyrene-b-poly(acrylic acid) block copolymer in dioxane/water and dioxane/THF/water mixtures. We then examine the ability of additives (such as NaCl, HCl, or NaOH), solvent composition, and hydrophilic block length to control vesicle size. Using turbidity measurements and transmission electron microscopy (TEM) we show that larger vesicles can be prepared from a given copolymer by adding NaCl or HCl, while adding NaOH yields smaller vesicles. The solvent composition (ratio of dioxane to THF, as well as the water content) can also determine the vesicle size. From a given copolymer, smaller vesicles can be prepared by increasing the THF content in the THF/dioxane solvent mixture. In a given solvent mixture, vesicle size increases with water content, but such an increase is most p...
TL;DR: A method in which hydroxyl radicals generated by a rapid-UV irradiation of a 15% hydrogen peroxide solution were utilized to oxidize specific amino acid side chains of two model proteins, according to the residues' chemical reactivities and the solvent accessibility of the reactive carbons and sulfurs in the residue is reported.
Abstract: Protein surfaces are important in most biological processes, including protein−protein interactions, enzymatic catalysis, and protein−ligand binding. We report a method in which hydroxyl radicals generated by a rapid-UV irradiation of a 15% hydrogen peroxide solution were utilized to oxidize specific amino acid side chains of two model proteins (lysozyme, β-lactoglobulin A), according to the residues' chemical reactivities and the solvent accessibility of the reactive carbons and sulfurs in the residue. Oxidized peptides generated by tryptic digestion were identified by electrospray-Fourier transform mass spectrometry. The specific sites of the stable modification were then identified by reverse-phase liquid chromatography coupled to quadropole ion trap tandem mass spectrometry. The solvent accessibility of the residue was shown to directly affect the rate of oxidation by this method (with the exception of methionine), supporting its use as a rapid measure of the solvent accessibility of specific residues...
TL;DR: It is clearly shown that macroscopic gelation can be related to a solvent polar solubility parameter for this system and the role of the solvent environment in terms of dendron--dendron intermolecular hydrogen bonding and its impact on the supramolecular chiral organization of the assembled superstructure is demonstrated.
Abstract: The self-assembly of diaminododecane with dendritic l-lysine-based peptides to form gel-phase materials was investigated in a range of different solvents. The degree of structuring was modulated by the solvent employed, an effect which induced subtle changes in the mesoscale aggregate morphology and macroscopic behavior of the self-assembled state. In this paper a range of different solvent parameters are investigated, and it is clearly shown that macroscopic gelation can be related to a solvent polar solubility parameter for this system. The results also show a dependence on Kamlet-Taft hydrogen bonding parameters, and this clearly demonstrates the role of the solvent environment in terms of dendron--dendron intermolecular hydrogen bonding and its impact on the supramolecular chiral organization of the assembled superstructure.
TL;DR: In this paper, a new methodology was developed to synthesize uniform rutile (α-TiO2) nanocrystals by the thermohydrolysis of titanium(IV) chloride in hydrochloric acid−alcohol aqueous solutions at 40−90 °C.
Abstract: A new methodology was developed to synthesize uniform rutile (α-TiO2) nanocrystals by the thermohydrolysis of titanium(IV) chloride in hydrochloric acid−alcohol aqueous solutions at 40−90 °C. Depending on the acidity, the solvent used, and the aging temperature, rod-shaped rutile nanocrystals in sizes ranging from ∼100 nm to 800 nm were obtained. Nanocrystal size and shape are shown to be strongly and systematically related to the type and the concentration of alcohol used in the alcohol−water solvent, as well as the presence or absence of both cationic and anionic surfactants. No other titania phases, such as anatase or brookite, were detected using X-ray diffraction, transmission electron microscopy, and Raman spectroscopy.
TL;DR: The SPARC self-interaction solvation models that describe the intermolecular interaction between like molecules (solute-solute or solvent-solvent) were extended to quantify solute solvent interaction energy in order to estimate the activity coefficient in almost any solvent as discussed by the authors.
Abstract: Solvation models, based on fundamental chemical structure theory, were developed in the SPARC mechanistic tool box to predict a large array of physical properties of organic compounds in water and in non-aqueous solvents strictly from molecular structure. The SPARC self-interaction solvation models that describe the intermolecular interaction between like molecules (solute-solute or solvent-solvent) were extended to quantify solute-solvent interaction energy in order to estimate the activity coefficient in almost any solvent. Solvation models that include dispersion, induction, dipole-dipole and hydrogen bonding interactions are used to describe the intermolecular interaction upon placing an organic solute molecule in any single or mixed solvent system. In addition to estimation of the activity coefficient for 2674 organic compounds, these solvation models were validated on solubility and liquid/liquid distribution coefficient in more than 163 solvents including water. The RMS deviations of the calculated versus observed activity coefficients, solubilities and liquid/liquid distribution coefficients were 0.272 log mole fraction, 0.487 log mole fraction and 0.44 log units, respectively.
TL;DR: This study aims to determine the relevant parameters controlling the organophilic montmorillonite dispersion in various organic solvents which can be used as dispersion media for polymer coatings.
TL;DR: A UV-responsive organic molecule was added to the oil phase, prior to emulsification, to investigate the release of a model active ingredient from the microcapsules to reduce both the release rate and the yield of the active ingredient.
Abstract: Microcapsules with an oil core surrounded by a polymeric shell have been prepared by the controlled phase separation of polymer dissolved within the oil droplets of an oil-in-water emulsion. The dispersed oil phase consists of the shell polymer (polystyrene), a good solvent for the polymer (dichloromethane), and a poor solvent for the polymer (typically hexadecane). Removal of the good solvent results in phase separation of the polymer within the oil droplets. If the three interfacial tensions between the core oil, the shell-forming polymer, and the continuous phase are of the required relative magnitudes, a polymer shell forms surrounding the poor solvent. A UV-responsive organic molecule was added to the oil phase, prior to emulsification, to investigate the release of a model active ingredient from the microcapsules. This molecule should be soluble in the organic core but also have some water solubility to provide a driving force for release into the continuous aqueous phase. As the release rate of the active ingredient is a function of the thickness of the polymeric shell, for controlled release applications, it is necessary to control this parameter. For the preparative method described here, the thickness of the shell formed is directly related to the mass of polymer dissolved in the oil phase. The rate of volatile solvent removal influences the porosity of the polymer shell. Rapid evaporation leads to cracks in the shell and a relatively fast release rate of the active ingredient. If a more gentle evaporation method is employed, the porosity of the polymer shell is decreased, resulting in a reduction in release rate. Cross-linking the polymer shell after capsule formation was also found to decrease both the release rate and the yield of the active ingredient. The nature of the oil core also affected the release yield.
TL;DR: In this article, the flux performance of organic solvents through a polydimethylsiloxane (PDMS) composite membrane was examined and it was suggested that the mechanism has a greater influence at higher pressures and the modus operandi is supported by the nonseparation of binary solvent mixtures and a dependency on viscosity and membrane thickness.
TL;DR: A series of poly(alkyl methacrylate)s that contained either pendant carboxylic acid or self-complementary multiple hydrogen bonding (SCMHB) groups were synthesized to determine the influence of intermolecular associations on solution rheology and electrospinning performance.