Mole Fraction Of Dimethyl Sulfoxide Research Articles

Ionic Pairing and Selective Solvation of Butylmethylimidazolium Chloride Ion Pairs in DMSO-Water Mixtures: A Comprehensive Examination via Molecular Dynamics Simulations and Potentials of Mean Force Analysis.

Ionic liquids (ILs) with dimethyl sulfoxide (DMSO) and water act as a promising solvent medium for the dissolution of cellulose in an efficient manner. To develop a proper solvent system, it is really important to understand the thermodynamics of the molecular solutions consisting of ILs, DMSO, and water. The ion-pairing propensity of the ILs in the presence of DMSO and water plays a crucial role in governing the property of the solvent mixtures. Employing all-atom molecular dynamics simulations, we estimate the potentials of mean force between BMIM+ and Cl- ions in DMSO-water mixtures. Analysis reveals a significant increase in the thermodynamic stability of both contact ion pair (CIP) and solvent-assisted ion pair (SAIP) states with a rising DMSO mole fraction. Thermodynamic assessments highlight the entropic stabilization of CIP states and SAIP states in pure water, in DMSO-water mixtures, and in pure DMSO. The structural analysis reveals that in comparison to the DMSO local density, the local water density is relatively very high around ion pairs, more specifically in the solvation shell of a chloride ion. Preferential binding coefficients also consistently indicate exclusion of DMSO from the ion pair in DMSO-water mixtures. To enhance our understanding regarding the solvent molecules kinetics around the ion pairs, the survival probabilities of DMSO and water are computed. The calculations reveal that the water molecules prefer a prolonged stay in the solvation shell of Cl- ions.

Dimethyl sulfoxide fosters larger micelles of docusate sodium in the mixed solutions with water

Docusate sodium also referred to as sodium bis(2-ethylhexyl)sulfosuccinate and dioctyl sulfosuccinate sodium (AOT) represents a green salt with proven potential across pharmacy, biology, and medicine. Physicochemical understanding of its inherent structural patterns, transport properties, and phase behavior in solutions is a challenging but essential endeavor. We hereby report conductometry, surface tension, density, and dynamic light scattering measurements of AOT in the dimethyl sulfoxide (DMSO)-water mixtures. The ab initio simulations are used to shed light on the electron density distributions and non-covalent interactions in the systems of our interest. We determine critical micelle concentration (CMC) and thermodynamic parameters of micellization (Gibbs free energy, enthalpy, and entropy) using the conductometry data at 298.15, 303.15, 308.15, 313.15, and 318.15 K. The CMC of AOT increases as DMSO mole fraction in the DMSO-water mixture increases. Negative free energies of micellization are observed over the entire investigated temperature range. Furthermore, higher contents of DMSO foster micellization gradually.The high contents of DMSO (X > 0.3) in the DMSO-water mixtures lead to abrupt changes in CMC and thermodynamics of AOT micellization. We link such changes to the formation of the DMSO self-associates and the associated structural changes in the liquid phase. The dynamic light scattering measurements reveal that larger micellar agglomerates and multilamellar AOT vesicles emerge at high DMSO fractions. The reported data fosters the thoughtful design of practically important systems in medicine.

Sensing non-ideal microheterogeneity in binary mixtures of dimethyl sulfoxide and water

We present a microscopic study of water–dimethyl sulfoxide (DMSO) binary mixtures using optical tweezers and thermal lens techniques. Binary mixtures of DMSO with water show anomalous behavior due to the specific hydrogen bonding ability of DMSO. We use a tightly focused femtosecond laser at a low average power to optically trap microspheres with diameters of 1 micron for use as probes. The binary mixture exhibits various viscosities, depending on its composition ratio, and hence different trapped particle characteristic frequencies (corner frequencies) due to Brownian motion. The power spectrum density method is used to obtain the corner frequency from forward-scattered data. Thus, using low-power optical tweezer experiments, we find that the maximum viscosity occurs at a DMSO mole fraction of 0.276. At higher powers, the propensity for trapping is highly diminished. It may be surprising to note that these viscosity values obtained from the corner frequencies do not exactly match those published in the literature. However, this deviation can be attributed to the thermal behavior of the binary mixture, which affects the Brownian motion and hence the obtained viscosity values. Studies at the microscopic level can thus provide a newer perspective on these already important binary mixtures. Intensity-dependent measurements further confirm the contribution of thermal effects in this study.

Cellulose Dissolution in Mixtures of Ionic Liquids and Dimethyl Sulfoxide: A Quantitative Assessment of the Relative Importance of Temperature and Composition of the Binary Solvent.

We studied the dissolution of microcrystalline cellulose (MCC) in binary mixtures of dimethyl sulfoxide (DMSO) and the ionic liquids: allylbenzyldimethylammonium acetate; 1-(2-methoxyethyl)-3-methylimidazolium acetate; 1,8-diazabicyclo [5.4.0]undec-7-ene-8-ium acetate; tetramethylguanidinium acetate. Using chemometrics, we determined the dependence of the mass fraction (in %) of dissolved cellulose (MCC-m%) on the temperature, T = 40, 60, and 80 °C, and the mole fraction of DMSO, χDMSO = 0.4, 0.6, and 0.8. We derived equations that quantified the dependence of MCC-m% on T and χDMSO. Cellulose dissolution increased as a function of increasing both variables; the contribution of χDMSO was larger than that of T in some cases. Solvent empirical polarity was qualitatively employed to rationalize the cellulose dissolution efficiency of the solvent. Using the solvatochromic probe 2,6-dichloro-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (WB), we calculated the empirical polarity ET(WB) of cellobiose (a model for MCC) in ionic liquid (IL)–DMSO mixtures. The ET(WB) correlated perfectly with T (fixed χDMSO) and with χDMSO (fixed T). These results show that there is ground for using medium empirical polarity to assess cellulose dissolution efficiency. We calculated values of MCC-m% under conditions other than those employed to generate the statistical model and determined the corresponding MCC-m% experimentally. The excellent agreement between both values shows the robustness of the statistical model and the usefulness of our approach to predict cellulose dissolution, thus saving time, labor, and material.

Understanding cellulose dissolution in ionic liquid-dimethyl sulfoxide binary mixtures: Quantification of the relative importance of hydrogen bonding and hydrophobic interactions

We studied the dissolution of microcrystalline cellulose (MCC) in mixtures of dimethyl sulfoxide (DMSO) with 32 ionic liquids (ILs), at a fixed temperature (70 °C) and mole fraction of DMSO (χDMSO = 0.6). Under these conditions, employing a recommended dissolution protocol, MCC dissolved in 19 IL-DMSO mixtures. In order to access quantitatively the relative importance (to biopolymer dissolution) of cellulose-solvent interactions, we correlated the mass fraction of dissolved cellulose (MCC-m%) with physicochemical properties of these mixtures. The solvent descriptors that gave the best correlations are Lewis acidity and Lewis basicity (calculated from the UV–Vis spectra of solvatochromic probes), the molar volume of the IL, and the Lorentz-Lorenz refractive index function of the IL-DMSO mixtures. This result is similar to that observed when solvent empirical polarities of these binary mixtures were correlated with the same descriptors. The multi-parameter correlations quantify, for the first time, the relative importance of cellulose-solvent interactions. Our results agree with the established opinion that an efficient cellulose solvent should disrupt the inter- and intramolecular hydrogen bonding in cellulose, and the hydrophobic interactions present due to the amphiphilic nature of the biopolymer.

Phenformin in aqueous co-solvent mixtures of N,N-dimethylformamide, ethanol, N-methylpyrrolidone and dimethyl sulfoxide: Solubility, solvent effect and preferential solvation

The equilibrium mole fraction solubility of phenformin in four co-solvent mixtures of N,N-dimethylformamide (DMF) + water (2), ethanol (1) + water (2) and N-methylpyrrolidone (NMP, 1) + water (2) at temperatures from 278.15 K to 323.15 K and dimethyl sulfoxide (DMSO) (1) + water (2) at temperatures from 293.15 K to 323.15 K were determined via the saturation shake-flask technique. The maximum solubility values were observed in the neat co-solvents of DMF (DMSO, NMP and ethanol). Through the Jouyban-Acree model, the phenformin solubility in the four solvent mixtures was well correlated attaining RAD values less than 3.21% and RMSD values less than 4.84 × 10−4. To describe how solvent affect the solubility, the obtained solubility data were introduced into the linear solvation energy relationships model by taking the cavity term and KAT parameters as solvent’s descriptors. It was shown that the cavity term and hydrogen bond acidity of solvent play the key role on the solubility variation in aqueous DMF, DMSO, ethanol and NMP mixtures. What's more, the quantitative values for local mole fractions of DMSO (DMF, ethanol or NMP) and water around the drug phenformin were calculated by the Inverse Kirkwood–Buff integrals method based on solubility data. Phenformin was preferentially solvated by water in the DMSO/DMSO (1) + water (2) mixtures with compositions 0 < x1 < 0.20 and NMP (1) + water (2) mixture with compositions 0 < x1 < 0.16; while for the ethanol (1) + water (2) mixture with compositions 0.25 < x1 < 1, phenformin is preferentially solvated ethanol.

Dielectric spectrum and structure of aqueous solutions of dimethyl sulfoxide

Frequency measurements of aqueous solutions of dimethyl sulfoxide (DMSO) were carried out in the range of 0.5-36.5 GHz at temperatures 293-323 K. Relaxation spectra were used to determine dipole relaxation times and the distribution parameter of these times, which were in good agreement with the Cole-Cole model. The thermodynamic characteristics of dipole relaxation and viscous flow were calculated based on the obtained results and found to be similar to the energy characteristics of the hydrogen bond and to have maximum values in the region of 0.3-0.4 mole fractions of DMSO. Kinetics of intermolecular interaction suggesting the formation in mixtures of 1 ∶ 2 and 2 ∶ 1 DMSO-Н2О complexes were studied.

Solubility of carbon dioxide in binary mixtures of dimethyl sulfoxide and ethylene glycol: LFER analysis

The solubility of carbon dioxide was determined in dimethyl sulfoxide, ethylene glycol, and their binary mixtures at the temperatures ranging from 298.15 Kto 328.15 K and the pressures ranging from (0 to 6) bar (0 to 0.6 MPa). It was shown that the solubility of CO2 increased with the increasing of pressure while decreased with the increasing of temperature. The Henry’s constants and thermodynamic properties of solution were calculated from the solubility data. The solubility and Henry’s constant of CO2 in the solvent mixtures increased with increasing the mole fraction of dimethyl sulfoxide. Finally, the dependence of CO2 solubility on solvent properties was investigated using the linear Gibbs energy relationship method. Results showed that solute-solvent interactions in the scale of polarity/polarizability and hydrogen bond acceptor ability of the solvent were the main parameters which control the solubility of CO2 in the solvents.

Solvation properties of raft-like model membranes

Dimethyl sulfoxide (DMSO) is a universal water-soluble solvent widely used in many biotechnological and medical applications, such as cells cryopreservation, and for the treatment of different human diseases (e.g. amyloidosis). Despite the great number of reported studies, the effects of DMSO on the physico-chemical properties of biological membranes are poorly understood. Often, these studies are limited to model membranes composed of phosphatidylcholines (PCs) and cholesterol (Chol). In this work, we explored the effect of DMSO on liposomes composed of the natural egg sphingomyelin (ESM) and Chol as raft-like model membranes.With a multi-technique approach we probe the structure and the thermal stability of ESM/Chol bilayer at different Chol mole fractions. In particular, we investigate the ESM-solvent interactions to clarify the role of DMSO in perturbing the solvating conditions of lipid vesicles and show that the addition of DMSO increases the thermal stability of vesicles. An increase of transition temperature, a decrease of both enthalpy and entropy as well as a decrease of the cooperativity of the gel to liquid phase transition are observed at 0.1 DMSO mole fraction. Fluorescence experiments with the probe Laurdan and FTIR spectra strongly indicate that DMSO exerts a dehydration effect on the membrane. Besides, FTIR measurements with tungsten hexacarbonyl, in combination with fluorescence data of the probe NBD-PE, indicate that DMSO promotes the formation of a highly packed membrane by reducing the thickness of the membrane.

Solubility of chloroxine in aqueous co-solvent mixtures of N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and 1,4-dioxane: Determination, solvent effect and preferential solvation analysis

The equilibrium solubility of amorphous chloroxine in four co-solvent mixtures of dimethyl sulfoxide (DMSO) (1) + water (2), N,N-dimethylformamide (DMF) (1) + water (2), N-methyl-2-pyrrolidone (NMP) (1) + water (2) and 1,4-dioxane (1) + water (2) is reported. Experiments were performed by using the saturation shake-flask technique over the temperature range from (293.15 to 333.15) K. The maximum solubility was observed in neat DMF (DMSO, NMP or 1,4-dioxane) for the four co-solvent mixtures. By using the Jouyban-Acree model, the chloroxine solubility was well correlated obtaining RAD values lower than 3.64% and RMSD values lower than 8.82 × 10−6. Quantitative values for the local mole fraction of DMSO (DMF, NMP or 1,4-dioxane) and water around the chloroxine were computed by using the Inverse Kirkwood–Buff integrals method applied to the determined solubility data. Chloroxine was preferentially solvated by water for the studied mixtures in water-rich compositions; while within intermediate and co-solvent-rich compositions, chloroxine is preferentially solvated by DMSO (DMF, NMP or 1,4-dioxane) in DMSO (DMF, NMP or 1,4-dioxane) + water mixtures. Moreover, in the light of Kamlet and Taft linear solvation energy relationships model, the co-solvency effect was rationalized, and the relative importance of solvent-solute and solvent-solvent interactions was recognized. It was shown that the change in solvent-solvent interaction energy accounted by cavity term governed the solubility variation of chloroxine in all aqueous mixtures.

Solubility modelling and thermodynamic aspect of d-aspartic acid in aqueous co-solvent mixtures of N-methyl-2-pyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide and 1.4-dioxane

The solubility of d-aspartic acid in co-solvent mixtures of dimethyl sulfoxide (DMSO) (1) + water (2), N,N-dimethylformamide (DMF) (1) + water (2), N-methyl-2-pyrrolidone (NMP) (1) + water (2) and 1,4-dioxane (1) + water (2) at the temperatures from (288.15/298.15 to 333.15) K was reported. Experiments were performed through the saturation shake-flask technique. The maximum solubility values were observed in the neat DMF (DMSO, NMP and 1,4-dioxane) for the four aqueous co-solvent mixtures. Through the Jouyban-Acree model, the d-aspartic acid solubility was well correlated attaining RAD values less than 2.55% and RMSD values less than 2.81 × 10−4. The local mole fractions of DMSO (DMF, NMP or 1,4-dioxane) and water nearby the d-aspartic acid were analyzed through the Inverse Kirkwood–Buff integrals method. d-Aspartic acid was preferentially solvated by water in water-rich compositions; while within intermediate and co-solvent-rich compositions, d-aspartic acid was preferentially solvated by DMF (NMP or 1,4-dioxane) in DMF (NMP or 1,4-dioxane) + water mixtures. In addition, the model of Kamlet and Taft linear solvation energy relationships was employed in order to rationalize the co-solvency effect and to identify its main components. It was found that the work needed for breaking solvent-solvent interactions presented by cavity term mainly controlled the solubility enhancement over the entire composition range in all the aqueous binary mixtures.

Solute–Solvent and Solvent–Solvent Interactions and Preferential Solvation of 1,1-Diamino-2,2-dinitroethylene in Aqueous Co-solvent Mixtures of N,N-Dimethylformamide and Dimethyl Sulfoxide

The effects of solvent properties on 1,1-diamino-2,2-dinitroethylene (FOX-7) solubility were investigated from the solubility values in aqueous co-solvent mixtures of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in terms of the linear solvation energy relationships with use of mathCAD software. For both aqueous mixtures, the main effect of hydrogen bond basicity was observed based on the solubility variation of FOX-7. The preferential solvation (the difference in composition between the solvation shell of the solute and the bulk composition in a mixture) of FOX-7 in the two aqueous of co-solvent solutions were investigated by using the method of inverse Kirkwood–Buff integrals (IKBI). The values of the preferential solvation parameters (δx1,3) were negative in water-rich mixtures, which are − 3.103×10−2 to − 2.936 × 10−2 for DMF (1) + water (2) mixtures and − 4.470 × 10−2 to − 3.995 × 10−2 for DMSO (1) + water (2) mixtures. However, in the co-solvent compositions ranging from 0.19 or 0.21 to 1 in mole fraction of DMF or DMSO, positive values of δx1,3 were observed. The preference of FOX-7 in water-rich mixtures can be explained based on the higher acidic behavior of FOX-7 molecules, which interact with the proton–acceptor functional groups of DMF and DMSO. KAT-LSER analysis showed that only the hydrogen-bond acceptor basicity of solvents played an important role on the FOX-7 solubility owing to its two amino functional groups. The squared correlation coefficient and F-statistic values are 0.98 and 314 for DMF + water mixture, and 0.96 and 130 for DMSO + water mixture, respectively.

Equilibrium solubility determination, modelling and thermodynamic aspects of 6-chloroguanine in aqueous co-solvent mixtures of N,N-dimethylformamide, isopropanol, 1,4-dioxane and dimethyl sulfoxide

The equilibrium solubility of 6-chloroguanine in four co-solvent mixtures of dimethyl sulfoxide (DMSO) (1) + water (2), N,N-dimethylformamide (DMF) + water (2), isopropanol (1) + water (2) and 1,4-dioxane (1) + water (2) over the temperature range from (278.15 to 333.15) K were reported. At the same temperature and composition of DMSO, DMF, isopropanol or 1,4-dioxane, the mole fraction solubility of 6-chloroguanine was highest in DMSO (1) + water (2) mixtures, and lowest in 1,4-dioxane (1) + water (2) mixtures. By using the Jouyban-Acree, van’t Hoff-Jouyban-Acree and Apelblat-Jouyban-Acree models, 6-chloroguanine solubility was well correlated obtaining RAD lower than 5.83% and RMSD lower than 4.82 × 10−4. Quantitative values for the local mole fraction of DMSO (DMF, isopropanol or 1,4-dioxane) and water around the 6-chloroguanine were computed by using the Inverse Kirkwood–Buff integrals method applied to the determined solubility data. For the DMF (1) + water (2) mixture with composition 0.20 < x1 < 0.69, DMSO (1) + water (2) mixture with composition 0.20 < x1 < 1 and 1,4-dioxane (1) + water (2) mixture with composition 0.18 < x1 < 0.35, 6-chloroguanine is preferentially solvated by the co-solvent. For the isopropanol (1) + water (2) mixture with composition 0.25 < x1 < 0.70, 6-chloroguanine is preferentially solvated neither by isopropanol nor by water. However, in the other regions for the four co-solvent mixtures, 6-chloroguanine is preferentially solvated by water. The dissolution process of 6-chloroguanine in solvent solutions was endothermic. Furthermore, transfer Gibbs energy (ΔtrG°), enthalpy (ΔtrH°), and entropy (ΔtrS°) were calculated, demonstrating that the solubilization capacity was more favorable with the increase in the co-solvent concentration.

Cooperative Order–Disorder Transition of Carboxylated Schizophyllan in Water–Dimethylsulfoxide Mixtures

Carboxylated schizophyllan ("sclerox") is a chemically modified polysaccharide obtained by partial periodate oxidation and subsequent chlorite oxidation of schizophyllan, a water-soluble neutral polysaccharide having a β-1,3-linked glucan backbone and a β-1,6-linked d-glucose residue side chain at every third residue of the main chain. The triple helix of schizophyllan in water has a cooperative order-disorder transition associated with the side chains. The transition is strongly affected by the presence (mole fraction) of dimethylsulfoxide (DMSO). In the present study, the solvent effects on the order-disorder transition of sclerox with different degrees of carboxylation (DS) in water-DMSO mixtures were investigated with differential scanning calorimetry and optical rotation. The transition temperature ( Tr) and transition enthalpy (Δ Hr) strongly depended on the mole fraction of DMSO ( xD). Data were further analyzed with the statistical theory for the linear cooperative transition, taking into account the solvent effect, where DMSO molecules are selectively associated with the unmodified side chains. The modified side chain does not contribute to the transition; hence, Δ Hr decreases with increasing DS. The dependence of Tr on the DMSO content becomes weaker than that for unmodified schizophyllan. The theoretical analyses indicated that the number of sites binding with the DMSO molecule and the successive ordered sequence of the ordered unit of the triple helix are changed by carboxylation.

Heat Effect of the Protonation of Glycine and the Enthalpies of Resolvation of Participating Chemical Species in Water–Dimethylsulfoxide Solvent Mixtures

Enthalpies of the protonation of glycine in water‒dimethylsulfoxide (DMSO) mixed solvents are determined calorimetrically in the range of DMSO mole fractions of 0.0 to 0.9, at T = 298.15 K and an ionic strength μ = 0.3 (NaClO4). It is established that the protonation of glycine becomes more exothermic with an increasing mole fraction of DMSO, and the enthalpies of resolvation of glycine and glycinium ions in water‒DMSO solvent mixtures are calculated. It is shown that the small changes in the enthalpy of protonation observed at low mole fractions of DMSO are caused by the contributions from the solvation of proton and protonated glycine cancelling each other out. The enthalpy term of the Gibbs energy of the reaction leading to the formation of glycinium ion is estimated along with the enthalpy of resolvation of the reacting species in the water‒DMSO mixed solvent.

Dimethyl sulfoxide-induced dehydration of the intermembrane space of dipalmitoylphosphatidylcholine multilamellar vesicles: Neutron and synchrotron diffraction study

Small-angle neutron scattering spectra of a polydispersed population of dipalmitoylphosphatidylcholine (DPPC) unilamellar vesicles in heavy water in the presence of dimethyl sulfoxide (DMSO) are analyzed by means of the separated form-factor method. An increase in the mole fraction of DMSO in water from 0 to 15% was shown to lead to an increase in the thickness of the bilayer to the characteristics repeat distances of DPPC multilamellar membranes. This fact is indicative of dehydration of the intermembrane space and a steric contact between adjacent DPPC bilayers at 15% mole fraction of DMSO.

Probing the replacement of water by dimethyl sulfoxide in the hydration shell of N-methylacetamide by FTIR-spectroscopy

The influence of dimethyl sulfoxide (DMSO) on the hydration of a peptide group has been explored by measuring the FTIR spectrum of N-methylacetamide in different mixtures of DMSO and D2O. An analysis of the amide I’ profile indicates two processes. For DMSO mole fractions between 0 and 0.5, the hydration shell on the side of the carbonyl group is systematically perturbed, which leads to a destabilization and eventual elimination of the hydrogen bonding between the carbonyl group and D2O. Upon further increasing the mole fraction of DMSO, water on the amide group side of the peptide is completely replaced by DMSO and the NH⇋ND exchange is significantly impeded. In mixtures with a very high fraction of DMSO, NMA with and without or weak hydrogen bonding to a DMSO molecule coexist with the latter configuration being clearly dominant in pure DMSO. Our results corroborate the recently debated notion that DMSO functions as a chaotropic cosolvent even at low fractions in that it exhibits preferential binding of water to the solute and by perturbing the stability of the peptide-water entity. They also reveal a rather fast exchange between different peptide-solvent complexes at low DMSO concentrations.

Local structure of dilute aqueous DMSO solutions, as seen from molecular dynamics simulations.

The information about the structure of dimethyl sulfoxide (DMSO)-water mixtures at relatively low DMSO mole fractions is an important step in order to understand their cryoprotective properties as well as the solvation process of proteins and amino acids. Classical MD simulations, using the potential model combination that best reproduces the free energy of mixing of these compounds, are used to analyze the local structure of DMSO-water mixtures at DMSO mole fractions below 0.2. Significant changes in the local structure of DMSO are observed around the DMSO mole fraction of 0.1. The array of evidence, based on the cluster and the metric and topological parameters of the Voronoi polyhedra distributions, indicates that these changes are associated with the simultaneous increase of the number of DMSO-water and decrease of water-water hydrogen bonds with increasing DMSO concentration. The inversion between the dominance of these two types of H-bonds occurs around XDMSO = 0.1, above which the DMSO-DMSO interactions also start playing an important role. In other words, below the DMSO mole fraction of 0.1, DMSO molecules are mainly solvated by water molecules, while above it, their solvation shell consists of a mixture of water and DMSO. The trigonal, tetrahedral, and trigonal bipyramidal distributions of water shift to lower corresponding order parameter values indicating the loosening of these orientations. Adding DMSO does not affect the hydrogen bonding between a reference water molecule and its first neighbor hydrogen bonded water molecules, while it increases the bent hydrogen bond geometry involving the second ones. The close-packed local structure of the third, fourth, and fifth water neighbors also is reinforced. In accordance with previous theoretical and experimental data, the hydrogen bonding between water and the first, the second, and the third DMSO neighbors is stronger than that with its corresponding water neighbors. At a given DMSO mole fraction, the behavior of the intensity of the high orientational order parameter values indicates that water molecules are more ordered in the vicinity of the hydrophilic group while their structure is close-packed near the hydrophobic group of DMSO.

Isobaric Vapor–Liquid Equilibrium for the Binary and Ternary System with Isobutyl Alcohol, Isobutyl Acetate and Dimethyl Sulfoxide at 101.3 kPa

The isobaric vapor–liquid equilibrium (VLE) data for the binary systems isobutyl alcohol + dimethyl sulfoxide (DMSO), isobutyl acetate + DMSO, and ternary system isobutyl alcohol + isobutyl acetate + DMSO were measured at 101.3 kPa. All of the binary VLE data passed Wisniak’s modifed Herington area test and Wisniak point and area test. Ternary VLE data passed Wisniak point test. The VLE data of binary systems were correlated with NRTL, UNIQUAC, and Wilson models. The ternary VLE behavior were successfully predicted by the correlated binary parameters. The VLE data for the binary and ternary systems predicted by the correlated interaction parameters were in good agreement with all the experimental data. The relative volatility of isobutyl acetate to isobutyl alcohol can be greatly increased by DMSO and the azeotropic point of isobutyl acetate and isobutyl alcohol will disappear if the mole fraction of DMSO is greater than 0.36. DMSO is a promising solvent for separating the azeotrope of isobutyl alcohol an...

The effect of dimethylsulfoxide on the dissociation process of physical complexes of polyacrylonitrile in N ,N -dimethylformamide

The physical properties and gelation behavior of polyacrylonitrile (PAN) solutions were investigated in mixed solvents of N,N-dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO). In the individual solubility parameters, DMSO had the polar term closer to PAN than DMF. The SAXS profiles and FT-IR spectra of 20 wt% PAN solutions confirmed that internal structure and intermolecular complex between nitrile groups were broken up by the DMSO molecules. The slope on Cole-Cole plot, a measure of the solution heterogeneity, was increased with the mole fraction of DMSO (XDMSO) via three distinct zones. The homogenization was particularly noticeable in Zone 1 (0.0 < XDMSO < 0.4) and Zone 3 (0.7 < XDMSO < 1.0). The Huggins constant and UV/vis absorbance at 268 nm of dilute solutions decreased sharply above the XDMSO of 0.7 in Zone 3. This indicated the marked increase of the PAN solubility by dissociating the intramolecular complex between nitrile groups. In Zone 1, the storage modulus of 20 wt% PAN solutions decreased but loss modulus remained almost constant with the XDMSO at the lower frequency below 1 rad/s, indicating the weakening of the true entanglement points possessing the intermolecular complexes. The mechanism represented that the intermolecular complexes between nitrile groups were dissociated by DMSO earlier than the intramolecular ones.