Preferential solvation of Brooker's merocyanine in binary solvent mixtures composed of formamides and hydroxylic solvents

The ET polarity values of 4-[(1-methyl-4(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (Brooker's merocyanine) were collected in mixed-solvent systems comprising a formamide [N,N-dimethylformamide (DMF), N-methylformamide (NMF) or formamide (FA)] and a hydroxylic (water, methanol, ethanol, propan-2-ol or butan-1-ol) solvent. Binary mixtures involving DMF and the other formamides (NMF and FA) as well as NMF and FA were also studied. These data were employed in the investigation of the preferential solvation (PS) of the probe. Each solvent system was analyzed in terms of both solute-solvent and solvent-solvent interactions. These latter interactions were responsible for the synergism observed in many binary mixtures. This synergistic behaviour was observed for DMF-propan-2-ol, DMF-butan-1-ol, FA-methanol, FA-ethanol and for the mixtures of the alcohols with NMF. All data were successfully fitted to a model based on solvent-exchange equilibria, which allowed the separation of the different contributions of the solvent species in the solvation shell of the dye. The results suggest that both hydrogen bonding and solvophobic interactions contribute to the formation of the solvent complexes responsible for the observed synergistic effects in the PS of the dye.     

Thermal decomposition of cyclic organic peroxides in pure solvents and binary solvent mixtures

The thermal decomposition reaction of acetone cyclic triperoxide, acetone cyclic diperoxide, 4‐heptanone cyclic diperoxide, and pinacolone cyclic diperoxide ca. 0.02 M was studied in pure solvents (acetone and 1‐propanol) and in binary mixtures of acetone/1‐propanol at 150°C. The kinetics of each system was explored by gas chromatography (GC) at different solvent compositions. The reactions showed a behavior accordingly with a pseudo‐first‐order kinetic law up to at least 90% peroxide decomposition. The main organic products derived from these thermolysis reactions were detected by GC analysis. Among them, the corresponding ketones, methane, ethane, and propane were the main identified products. The rates of decomposition of pinacolone diperoxide in the pure solvents were practically independent of the solvent characteristics, so it was of no interest to analyze its kinetic behavior in binary solvent mixtures. In acetone/1‐propanol mixtures, the solvation effect on the cyclic peroxides derived from 4‐heptanone and acetone molecules was slightly dominated by specific interactions between 1‐propanol and a diradical‐activated complex initially formed. This species was preferentially solvated by 1‐propanol instead of acetone. Specific interactions between the O atoms from the peroxidic bond and the H from the OH in 1‐propanol can be taken into account. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 347–353, 2010     

Solubilities of cinnamic acid esters in binary mixtures of ionic liquids and organic solvents

The solubilities of three cinnamic acid esters, namely, methyl ferulate, methyl p-coumarate, and methyl sinapate, have been measured in mixed solvent systems of tert-butanol with 1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIM][PF₆]), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM][BF₄]) and 1-methyl-3-octyl-imidazolium tetrafluoroborate ([OMIM][BF₄]) at 303.15 and 321.15 K, and in mixed solvent systems of ethyl acetate with [BMIM][BF₄] and [OMIM][BF₄] at 303.15 K. In eight cases, out of the 22 data sets, an additive behaviour of the solubility was observed, positive deviations from additivity were observed in six cases, a positive synergistic effect in five cases, and, finally, negative deviations from additivity in the remaining three cases. Prediction of the solubilities of the solutes in the various ternary systems was performed with the NRTL and UNIQUAC activity coefficient models. The binary interaction parameters of the models between solute and solvent molecules were taken from the literature. When the parameters between the solvent molecules are fitted to literature data, satisfactory predictions are not always obtained. On the other hand, very good predictions are obtained when only one of the two interaction parameters between the two solvent molecules is fitted to one single point of the solubility isotherm and the other interaction parameter is set equal to zero.     

Phase and interfacial behavior of partially miscible symmetric Lennard-Jones binary mixtures

We have carried out extensive equilibrium molecular-dynamics simulations to study quantitatively the topology of the temperature versus density phase diagrams and related interfacial phenomena in a partially miscible symmetric Lennard-Jones binary mixture. The topological features are studied as a function of miscibility parameter, alpha = epsilonAB/epsilonAA. Here epsilonAA = epsilonBB and epsilonAB stand for the parameters related to the attractive part of the intermolecular interactions for similar and dissimilar particles, respectively. When the miscibility varies in the range 0 < alpha < 1, a continuous critical line of consolute points Tcons(rho)--critical demixing transition line--appears. This line intersects the liquid-vapor coexistence curve at different positions depending on the values of alpha, yielding mainly three different topologies for the phase diagrams. These results are in qualitative agreement to those found previously for square-well and hard-core Yukawa binary mixtures. The main contributions of the present paper are (i) a quantitative analysis of the phase behavior and (ii) a detailed study of the liquid-liquid interfacial and liquid-vapor surface tensions, as function of temperature and miscibility as well as its relationship to the topological features of the phase diagrams.     

On the nematic-nematic phase transition in mixtures composed of sheet-shaped palladium organyls and apolar organic solvents

The three sheet-shaped palladium organyls 1a-c exhibit lyotropic nematic properties in apolar organic solvents. The occurrence of two nematic lyomesophases was verified by the investigation of the orientational properties of these liquid crystalline systems. In cells with obliquely deposited SiO_x layers, the director of the high temperature phase N₂ is aligned in a homogeneous, planar manner. In the low temperature phase N₁, a different orientational pattern is observed. The specific pattern type depends on the deposition conditions of the SiO_x layers. In samples homeotropically aligned in the N₂ phase, the director is tilted away from the cell normal after the transition into the N₁ phase. These changes of orientation are reversible. The experimental observations presented here support our proposed model for the structural change at the nematic-nematic phase transition.     

On the nematic-nematic phase transition in mixtures composed of sheet-shaped palladium organyls and apolar organic solvents

Abstract

The three sheet-shaped palladium organyls 1a-c exhibit lyotropic nematic properties in apolar organic solvents. The occurrence of two nematic lyomesophases was verified by the investigation of the orientational properties of these liquid crystalline systems. In cells with obliquely deposited SiO _x layers, the director of the high temperature phase N₂ is aligned in a homogeneous, planar manner. In the low temperature phase N₁, a different orientational pattern is observed. The specific pattern type depends on the deposition conditions of the SiO _x layers. In samples homeotropically aligned in the N₂ phase, the director is tilted away from the cell normal after the transition into the N₁ phase. These changes of orientation are reversible. The experimental observations presented here support our proposed model for the structural change at the nematic-nematic phase transition.     

Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents

Abstract  

Solvatochromic parameters (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E _T ^N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π* and β are nearly ideal for all solutions except for solutions of methanol with the IL. The applicability of nearly ideal combined binary solvent/Redlich–Kister equation was proved for the correlation of various solvatochromic parameters with solvent composition. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute–solvent and solvent–solvent interactions were applied to interpret the results.     

Solvatochromic parameters for binary mixtures of an ionic liquid with various protic molecular solvents

Abstract  Solvatochromic parameters (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E _T ^N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π* and β are nearly ideal for all solutions except for solutions of methanol with the IL. The applicability of nearly ideal combined binary solvent/Redlich–Kister equation was proved for the correlation of various solvatochromic parameters with solvent composition. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute–solvent and solvent–solvent interactions were applied to interpret the results. Graphical Abstract  Predicted values of solvatochromic parameters (SP) (E _T ^N, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) from the correlation equations versus its experimental values for binary mixtures of 2-hydroxyethylammonium formate with water, methanol, ethanol, propan-1-ol and propan-2-ol.      

Microstructure of poly(ethylene oxide) gels dispersed in various organic solvents

Ordered structure formed in gels of poly(ethylene oxide) (PEO) dispersed in various organic solvents has been investigated by means of infrared spectroscopy. In a cooled gel (below −35 °C) of PEO dispersed in a 1:1 mol/mol mixture of chloroform and carbon disulfide, a uniform (7/2) helical conformation is formed, in contrast to the distorted helix present in the monoclinic crystal modification. In a low-temperature range below −65 °C formation of a rigid polymer-solvent complex is suggested. The structure of the resultant gels as well as the gelation behavior are strongly dependent on solvent, reflecting the difference in the strength of polymer-solvent interactions.     

Phase behavior and self-organized structures of diglycerol monolaurate in different nonpolar organic solvents

Nonaqueous phase behavior and reverse micellar structures of diglycerol monolaurate (DGL) in different nonpolar organic solvents, such as n-decane, n-tetradecane, and n-hexadecane, have been studied over a wide range of compositions and temperatures. The equilibrium phases are identified by means of visual observation and small-angle X-ray scattering (SAXS). A solid phase present at lower temperature swells small amount of oils and transforms into a lamellar liquid crystalline structure at higher temperature. The melting temperature of the solid phase is virtually constant at all mixing ratios of the surfactant and oil. With the further increase of temperature, the liquid crystal transforms into an isotropic single-liquid phase near the surfactant axis, whereas there is a coexistence region of two isotropic phases near the solvent axis. The area of the two-liquid (II) phase region depends largely on the hydrocarbon chain length of the oils, the longer chain leading to the wider II area. Accordingly, the DGL surfactant is most miscible with decane, exhibiting a reduced miscibility with increasing solvent hydrocarbon chain length. Increasing temperature enhances the dissolution tendency of the surfactant in oil, where the two-liquid phase transforms into an isotropic single phase. SAXS analysis based on the GIFT technique is used to characterize the structure of the reverse micellar aggregates in the isotropic single-phase liquids. We have demonstrated that instead of changing polarity or a functional group of the solvent molecules, if we optimize the hydrophilic nature of the surfactant head group, the alkyl chain length of the solvent oils can serve as a tunable parameter of the micellar geometry. The hydrophilic surfactant DGL interestingly forms cylindrical micelles in nonpolar oils, decane, and tetradecane in the dilute region above the II phase region. The micellar size shows temperature dependence behavior, and the micellar length goes on increasing with decreasing temperature; eventually we found a signature of the onset of critical fluctuations in the deduced pair-distance distribution function near the phase separation line. The signature of the attractive interaction between the cylindrical reverse aggregates when a phase separation line is approached is likely to be a precursor of critical phenomenon. Doping with a trace of water results in a similar but more pronounced structural enhancement. The transfer free energy of diglycerol moiety from a hydrophilic environment to different hydrocarbon oils may account for these phenomena.     

Separation of organic binary mixtures by pervaporation

Pervaporation is a membrane separation process which has the inherent advantage of excellent selectivity for a number of mixtures that are otherwise difficult to separate (e.g. azeotropic mixtures or mixtures of liquids with only small differences in vapor pressures). Important parameters for pervaporation are the operating pressure on the permeate side and the temperature drop at the membrane interface caused by the phase change from liquid to vapor. This paper presents a mathematical model for the mass transport of binary mixtures within the membrane. The calculations are based on the transport equations of Shelden and co-workers [1]. These equations were solved without any simplifying assumptions and tested experimentally with benzene—cyclohexane mixtures. The limitations of the mathematical model and possible methods of improving it are discussed. The temperature drop at the membrane interface and its influence on the rate of permeation are also examined.     

Adhesive properties of binary mixtures of some ethylene copolymers

It is shown using the example of polyolefin thermoplasts that the value of adhesion strength is determined by the mechanical properties of a composition.     

Spectroscopic and thermodynamic studies of binary mixtures composed of nematogenic and non-nematogenic components

The effect of a non-nematic guest, tetracyanoethylene (TCNE), on the liquid-crystaline state of the host, 4-n-pentyl-4′-cyanobiphenyl (5CB), has been investigated. It was shown by absorption spectroscopy that TCNE forms a 1 : 1 charge transfer complex with 5CB in the nematic phase, similar to that in the isotropic solution. The effect of TCNE on the transition temperature was investigated by comparison with a normal guest, 2,3-dimethylbutane (DMB), which has a molecular volume comparable with that of TCNE but has no specific interaction with the host. TCNE was found to lower the transition temperature much more strikingly than DMB, suggesting the peculiar effect of complex formation. The theoretical background is given based on molecular field theory.     

Spectroscopic and thermodynamic studies of binary mixtures composed of nematogenic and non-nematogenic components

The effect of a non-nematic guest, tetracyanoethylene (TCNE), on the liquid-crystaline state of the host, 4-n-pentyl-4'-cyanobiphenyl (5CB), has been investigated. It was shown by absorption spectroscopy that TCNE forms a 1 : 1 charge transfer complex with 5CB in the nematic phase, similar to that in the isotropic solution. The effect of TCNE on the transition temperature was investigated by comparison with a normal guest, 2,3-dimethylbutane (DMB), which has a molecular volume comparable with that of TCNE but has no specific interaction with the host. TCNE was found to lower the transition temperature much more strikingly than DMB, suggesting the peculiar effect of complex formation. The theoretical background is given based on molecular field theory.     

Phase equilibria in binary mixtures of ethane and hexadecane

This paper reports experimental results of a study of the phase behaviour of binary mixtures of ethane + hexadecane. In the near-critical region of ethane liquid + vapour and solid hexadecane + liquid two-phase boundaries have been measured. Also the three-phase equilibrium solid hexadecane + liquid + vapour has been determined experimentally. The experimental data cover the complete mole fraction range. Pressures up to 18 MPa were applied and the investigation was performed in a temperature region from about 260 K up to 450 K.     

Phase diagrams of binary mixtures of biaxial nematogens

A mean field theory is used to describe nematic phases of binary mixtures of biaxial molecules. Using a general pseudopotential consistent with the D_2h symmetry of the constituent particles, the theory is used to calculate the elements of the order tensors necessary to describe the orientational order in binary mixtures in both uniaxial and biaxial nematic phases. For a single component, the model only requires one parameter, r₂, a ratio of anisotropic interaction strengths, to predict the temperature dependence of the four order parameters. The temperature dependence of the orientational distribution functions is illustrated for both rod-like and plate-like molecules. For binary mixtures, three anisotropic interaction strengths, r₁, r₂, and r₃, are needed to calculate the order parameters of both components as a function of concentration and temperature. The free energy is evaluated to predict the phase stability of the mixture. By systematically varying the anisotropic interaction strengths, temperature-concentration phase diagrams for a variety of molecular shapes are presented. The theoretical predictions suggest that binary mixtures of molecules with highly asymmetric shapes will display stable biaxial nematic phases.     

Ultrasonic study of binary aqueous mixtures of three common eutectic solvents

Ultrasonic velocities have been measured for different binary mixtures of common choline chloride-based deep eutectic solvents (DESs), namely, reline, glyceline and ethaline with water, in the range of temperature: 303.15–353.15 K. The experimental data measurements with different mole fractions of DES–water solutions were utilised in fitting four different models for speed of sound. These models correlate the speed of sound with some physical properties such as molar volumes, molar components sound velocity, densities, molecular weights, collision factors etc. A close match was obtained with these models with an average relative error of less than 4% for all data points used. It was observed that the ultrasonic velocity increases with the concentration of DES solvent and decreases with temperature. Moreover, this study roughly indicated that the intermolecular interactions in reline and ethaline aqueous mixtures exist in the form of disruption of dipole–dipole interactions (that varies considerably as a function of DES mixture composition and solution temperature). On the other hand, the interactions on the molecular level in glyceline aqueous solution are mainly due to dipole–dipole intermolecular forces.     

Phase behavior of binary symmetric mixtures in pillared slit-like pores: a density functional approach

Density functional approach is applied to study the phase behavior of symmetric binary Lennard-Jones(12,6) mixtures in pillared slit-like pores. Our focus is in the evaluation of the first-order phase transitions in adsorbed phases and lines delimiting mixed and demixed adsorbed phases. The scenario of phase changes is sensitive to the pore width, to the energy of fluid-solid interaction, the amount, and the length of the pillars. Quantitative trends and qualitative changes of the phase diagrams topology are examined depending on the values of these parameters. The presence of pillars provides additional excluded volume effects, besides the confinement due to the pore walls. The effects of attraction between fluid species and pillars counteract this additional confinement. We have observed that both the increasing surface pillar density and the augmenting strength of fluid-solid interactions can qualitatively change the phase diagrams topology for the model with sufficiently strong trends for demixing. If the length of pillars is sufficiently large comparing to the pore width at low temperatures, we observe additional phase transitions of the first and second order due to the symmetry breaking of the distribution of chain segments and fluid species with respect to the slit-like pore center. Re-entrant symmetry changes and additional critical points then are observed.     

New efficient reaction media for SET‐LRP produced from binary mixtures of organic solvents and H2O

SET‐LRP is mediated by a combination of solvent and ligand that promotes disproportionation of Cu(I)X into Cu(0) and Cu(II)X₂. Therefore, the diversity of solvents suitable for SET‐LRP is limited. SET‐LRP of MA in a library of solvents with different equilibrium constants for disproportionation of Cu(I)X such as DMSO, DMF, DMAC, EC, PC, EtOH, MeOH, methoxyethanol, NMP, acetone and in their binary mixtures with H₂O was examined. H₂O exhibits the highest equilibrium constant for disproportionation of Cu(I)X. The apparent rate constant of the polymerization exhibits a linear increase with the addition of H₂O. This is consistent with higher equilibrium constants for disproportionation generated by addition of H₂O to organic solvents. Furthermore, with the exception of alcohols and carbonates, the rate constant of polymerization in binary mixtures could be correlated with the Dimroth‐Reichardt solvent polarity parameter. This is consistent with the single‐electron transfer mechanism proposed for SET‐LRP that involves a polar transition state. These experiments demonstrate that the use of binary mixtures of solvents with H₂O provides a new, simple and efficient method for the elaboration of a large diversity of reaction media that are suitable for SET‐LRP even when one of the two solvents does not mediate disproportionation of Cu(I)X. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5577–5590, 2009     

Reactions of binary and ternary alkali metal carbonate mixtures with aluminium oxide

Reactions of binary and ternary alkali metal carbonate mixtures with aluminium oxide were studied by means of a derivatograph under different conditions. Reaction products were identified by X-ray diffraction.In the presence of binary and ternary carbonate, mixtures containing Li₂CO₃ the product was always-lithium metaaluminate, transforming to the-form at higher temperatures, while using only Li₂CO₃ the orthodialuminate could be obtained too.

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Zusammenfassung Die Reaktionen binärer und ternärer Alkalikarbonatmischungen mit Aluminiumoxid wurden mittels eines Derivatographen unter verschiedenen Bedingungen untersucht. Die Reaktionsprodukte wurden durch Röntgendiffraktion identifiziert.In Gegenwart Li₂CO₃-haltiger binärer und ternärer Karbonatmischungen war das Produkt stets -Lithium-meta-aluminat, das bei höheren Temperaturen in die-Form überging, während bei Einsatz von Li₂CO₃ auch Orthodialuminat erhalten werden konnte.

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Résumé On a étudié à l'aide d'un Derivatograph, sous diverses conditions, la réaction de mélanges binaires et ternaires des carbonates alcalins avec l'oxyde d'aluminium. L'identification des produits formés a été effectuée par diffraction des rayons X.Si les mélanges binaires et ternaires de carbonates contiennent du carbonate de lithium, il se forme toujours 1'-métaaluminate de lithium, qui, à température plus élevée, se transforme en la forme. Si la carbonate de lithium est utilisé seul, on peut obtenir aussi l'ortho-dialuminate.

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. - . , Li₂CO₃, - , -. Li₂CO₃, .