Phase Behavior Of Binary Mixtures Research Articles

Magnesium bis(trifluoromethanesulfonyl)amide complexes with triglyme and asymmetric homologues: phase behavior, coordination structures and melting point reduction.

The phase behavior of binary mixtures of triglyme (G3) and Mg[TFSA]2 (TFSA: bis(trifluoromethanesulfonyl)amide) was investigated, towards the development of a Mg2+-based room-temperature solvate ionic liquid (SIL) electrolyte. In a 1 : 1 molar ratio, G3 and Mg[TFSA]2 form a thermally stable complex (decomposition temperature, Td: 240 °C) with a melting point (Tm) of 70 °C, which is considerably lower than that of the analogous tetraglyme (G4) system (137 °C). X-ray crystallography of a single crystal of [Mg(G3)][TFSA]2 revealed that a single Mg2+ cation is coordinated by a single, distorted, tetradentate G3 molecule from one side, and two monodentate [TFSA]- anions, with transoid conformation, from the reverse side to form an ion pair. Raman spectra of [Mg(G3)][TFSA]2 in the molten state revealed the presence of different coordination structures, as the liquid exhibits changes in the vibrational modes corresponding to G3 and the [TFSA]- anion compared to those observed for the solid. Investigation of the ion pair stabilization energies by DFT calculations suggests that higher stability cation complexes and ion pairs co-exist in the molten state than those observed in the crystalline state. These results imply that the coordination structures of the ion pairs play a key role in providing SILs with low Tm. To decrease the Tm further, several asymmetric homologues of G3, which have higher conformational flexibility than G3, were investigated. Notably, a 1 : 1 mixture of Mg[TFSA]2 with G3Bu (where one of the terminal methyl groups of G3 is substituted for a butyl group) formed a thermally stable complex (Td: 251 °C) without any distinct Tm and showed reasonable ionic conductivity at room-temperature, indicating partial dissociation of ions. In this electrolyte, which showed high oxidative stability, quasi-reversible Mg deposition/dissolution was achieved, indicating that Mg2+-based room-temperature SILs can be utilized as a new class of Mg electrolyte.

Phase behavior of the polymer/drug system PLA/DEET: Effect of PLA molar mass on subambient liquid-liquid phase separation

The phase behavior of binary mixtures of non-crystallizable racemic poly (d, l-lactic acid) (PDLLA) and the mosquito-repellent/drug N,N-diethyl-3-methylbenzamide (DEET) was analyzed with respect to the effect of the polymer molar mass on the liquid-liquid (L–L) phase separation characteristics, by cloud-point measurements and differential scanning calorimetry. The PDLLA/DEET system shows a subambient upper critical solution temperature (UCST), with the critical temperature decreasing and critical polymer concentration increasing with decreasing molar mass of PDLLA. The obtained L–L phase separation curves were used to estimate the temperature-dependence of the interaction parameter, confirming that the enhanced miscibility of the system components in case of low molar mass PDLLA is due to increased entropy of mixing.

Binary Colloidal Crystal Films Grown by Vertical Evaporation of Silica Nanoparticle Suspensions

Despite intensive research efforts in the synthesis of binary colloidal crystals, the production of well ordered binary colloidal crystal films over large areas continues to be synthetically challenging. In this paper, we investigate the phase behavior of binary mixtures of l-arginine-stabilized 36 and 22 nm silica nanoparticles deposited as centimeter-scale thin films onto a vertical substrate via evaporative assembly. By adjusting the temperature and relative colloid composition under high humidity conditions, we controlled the order of the resultant colloidal crystal films. The domain size of the AB2 binary crystalline phase increased with an excess of small (B) particles and a very slow evaporation rate below 45 °C, with the best results obtained at 30° and 35 °C.

Phase Behavior of Binary Mixtures Containing Succinic Acid or Its Esters

This work provides experimental data and thermodynamic modeling on phase equilibria of binary mixtures that are relevant for esterification reactions. The components under investigation include water, succinic acid (SA), ethanol (EtOH), 1-butanol (1-BuOH), and the diesters of SA, namely, diethyl succinate (DES) and dibutyl succinate (DBS), respectively, as well as the organic solvents acetonitrile (ACN) and tetrahydrofuran (THF). Liquid–liquid equilibria (LLE) of water/DBS were measured at ambient pressure for temperatures between 313 and 353 K. Isobaric vapor–liquid equilibria (VLE) were measured for the binary systems ACN/DES, ACN/DBS, 1-BuOH/DBS, and THF/DBS at pressures of 10 or 20 or 30 kPa. Temperature ranges for the isobaric VLE varied between 300 and 500 K. The measured data and phase equilibria reported in literature were accurately modeled using perturbed-chain statistical associating fluid theory (PC-SAFT). For this purpose, pure-component PC-SAFT parameters, which were not already reported in ...

Induced Attraction between Polystyrene Colloidal Particles in a Binary Mixture with PNIPAM Colloidal Microgels.

We investigate the phase behaviors of binary mixtures of polystyrene (PS) hard-sphere and poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM) soft-sphere colloidal particles as a function of temperature. As the temperature increases, apparent attractions arise between the PS particles, to the point of clustering at the highest temperature. This attractive force is found to be due to the change in pH caused by the acrylic acid co-polymerized with the temperature-sensitive PNIPAM particles, which in turn collapses the sterical stabilizing surface layers on the PS particles. Our experiments provide a new way to tune colloidal interactions with temperature for particles that are otherwise insensitive to temperature variations.

Phase behavior of binary mixtures of three different 1,3‐diacylglycerols

Compared to triacylglycerol compositions, 1,3‐diacylglycerols (1,3‐DAG) have gained far less concern. Consequently, studying the mixing behavior of representative 1,3‐DAG components in palm‐based DAG oils such as 1,3‐dipalmitoyl‐sn‐glycerol (1,3‐PP), 1‐palmitoyl‐3‐oleoyl‐sn‐glycerol (1,3‐PO), and 1,3‐dioleoyl‐sn‐glycerol (1,3‐OO) is of critical interest. This study focused on the phase behavior of binary mixtures for 1,3‐PO/1,3‐OO, 1,3‐PP/1,3‐OO, and 1,3‐PO/1,3‐PP through polarized light microscopy (PLM) and differential scanning calorimetry (DSC) at 1 and 10°C/min cooling and melting rates. The kinetic phase diagrams of 1,3‐PO/1,3‐OO, 1,3‐PP/1,3‐OO, and 1,3‐PO/1,3‐PP constructed using melting DSC thermograms indicated that obvious eutectic behaviors were detected for 1,3‐PO/1,3‐OO and 1,3‐PO/1,3‐PP with eutectic composition at 0.2 × 1,3‐PO and 0.1 × 1,3‐PP, respectively, while 1,3‐PP/1,3‐OO showed an monotectic behavior. The simulation of the liquidus boundaries for two eutectic binary systems of 1,3‐PO/1,3‐OO and 1,3‐PO/1,3‐PP produced negative ρ values for all their segments apart from the region of 0 ≤ X1,3‐PP ≤ Xe at both cooling rates, which indicated that the molecular interactions between 1,3‐PO and 1,3‐OO or 1,3‐PO and 1,3‐PP in region of Xe ≤ X1,3‐PP ≤ 1 were inclined to favor the formation of mixed‐pairs. The PLM results exhibited that the variations in the microstructure were strongly affected by the adding components, especially apparent at compositions in proximity of the eutectic composition.Practical application: Palm‐based DAG oils have attracted much interest because of the unique properties. 1‐palmitoyl‐3‐oleoyl‐sn‐glycerol, 1,3‐dipalmitoyl‐sn‐glycerol, and 1,3‐dioleoyl‐sn‐glycerol are representative 1,3‐DAG components in palm‐based DAG oils. The study of the phase behaviors of these representative 1,3‐diacylglycerols will contribute to exploring the fractionation, phase development and crystallization of palm‐based DAG oils, which makes DAG oils even more interesting as functional oils with distinct physicochemical characteristics and nutritional advantages.DSC melting profiles of 1,3‐PO/1,3‐OO binary mixtures obtained at (a) 10°C/min and (b) 1°C/min heating rate and the corresponding binary phase diagrams. The result exhibits that the differing rates have an influence on the melting thermograms including the peak shapes, melting onset, and offset. Nevertheless, these differences are not to the degree of altering the sequence of phase transition of 1,3‐PO/1,3‐OO binary mixtures.

Phase behaviors of binary mixtures composed of electron-rich and electron-poor triphenylene discotic liquid crystals**Project supported by the National Natural Science Foundation of China (Grant Nos. 51273133 and 51443004).

Disk-like liquid crystals (DLCs) can self-assemble to ordered columnar mesophases and are intriguing one-dimensional organic semiconductors with high charge carrier mobility. To improve their applicable property of mesomorphic temperature ranges, we exploit the binary mixtures of electronic donor-acceptor DLC materials. The electron-rich 2,3,6,7,10,11-hexakis(alkoxy)triphenylenes (C4, C6, C8, C10, C12) and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated. The mesomorphism of the 1:1 (molar ratio) mixtures has been characterized by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and small angel x-ray scattering (SAXS). The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy (STM). The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures.

Dielectric, ferroelectric, and thermodynamic properties of silicone oil modified PVDF films for energy storage application

Silicone oil modified poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) films were fabricated by the blending, casting, and hot-molding methods. The dielectric constant was increased for the 7.4 wt. % and 17.0 wt. % silicone oil modified P(VDF-HFP) films, while the dielectric loss for all blend films are decreased. D-E loops of 7.4 wt. % and 17.0 wt. % silicone oil modified P(VDF-HFP) films become slimmer than the pristine P(VDF-HFP) films. The maximum discharged energy density of 10.3 J/cm3 was obtained in 7.4 wt. % silicone oil modified P(VDF-HFP) films at the external electric field of 398 kV/mm. The Gibbs energy, miscibility, and phase behavior of binary mixture of P(VDF-HFP) silicone oil were investigated using molecular simulations and the extended Flory–Huggins model revealing favorable interactions and compatibility between P(VDF-HFP) and silicone oil.

Thermal and Electrochemical Stability of Tetraglyme–Magnesium Bis(trifluoromethanesulfonyl)amide Complex: Electric Field Effect of Divalent Cation on Solvate Stability

Phase behavior of binary mixtures of tetraglyme (G4) and Mg[TFSA]2 (TFSA: bis(trifluoromethanesulfonyl)amide) was investigated. In a 1:1 molar ratio, G4 and Mg[TFSA]2 formed a stable complex with a melting point of 137 °C. X-ray crystallography of a single crystal of the complex grown from a G4-Mg[TFSA]2 binary mixture revealed that the G4 molecule wraps around Mg2+ to form a complex [Mg(G4)]2+ cation, and the two [TFSA]− anions also participate in the Mg2+ coordination in the crystal. The thermal stability of [Mg(G4)][TFSA]2 was examined by thermogravimetry, and it was found that the complex is stable up to 250 °C. Above 250 °C, desolvation of the Mg2+ ion takes place and G4 evaporates. On the other hand, the weight loss starts at around 140 °C in solutions containing excess G4 (n > 1 in Mg[TFSA]2:G4 = 1:n) due to the evaporation of free (uncoordinated) G4. The suppression of G4 volatility in the [Mg(G4)][TFSA]2 complex is attributed to strong electrostatic and induction interactions between divalent Mg2...

Binary mixtures of fatty acid methyl esters as phase change materials for low temperature applications

Incorporating phase change materials (PCMs) into concrete pavements has been suggested as a means to improve anti-icing practices by reducing the accumulation of snow and ice. This paper reports on the development of two PCMs composed of a binary mixture of fatty acid methyl esters (FAME) at their eutectic composition, which provide a solid–liquid phase transformation with thermal transition temperature slightly above 0 °C and with a high enthalpy of fusion. The phase behavior of binary mixtures of medium length saturated FAME at their eutectic composition demonstrated ideal properties for PCMs. The eutectic binary mixtures and corresponding thermal properties are: (1) methyl laurate (C12) + methyl myristate, xC12=0.77, and (2) methyl laurate + methyl palmitate, xC12=0.86 with eutectic melting temperatures and latent heats of fusion of 0.21 °C and 2.4 °C, and 174.3 J⋅g−1 and 166.5 J⋅g−1, respectively. Using differential scanning calorimetry, solid–liquid phase diagrams were created, indicating that the phase behavior of these binary mixtures at their eutectic compositions demonstrated useful thermal properties for PCMs. Current findings of this study indicate that these binary mixtures have the necessary properties to be a high performance PCM with the potential to reduce the levels of icing on concrete pavements.

The Phase Behavior of γ-Oryzanol and β-Sitosterol in Edible Oil.

The phase behavior of binary mixtures of γ-oryzanol and β-sitosterol and ternary mixtures of γ-oryzanol and β-sitosterol in sunflower oil was studied. Binary mixtures of γ-oryzanol and β-sitosterol show double-eutectic behavior. Complex phase behavior with two intermediate mixed solid phases was derived from differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) data, in which a compound that consists of γ-oryzanol and β-sitosterol molecules at a specific ratio can be formed. SAXS shows that the organization of γ-oryzanol and β-sitosterol in the mixed phases is different from the structure of tubules in ternary systems. Ternary mixtures including sunflower oil do not show a sudden structural transition from the compound to a tubule, but a gradual transition occurs as γ-oryzanol and β-sitosterol are diluted in edible oil. The same behavior is observed when melting binary mixtures of γ-oryzanol and β-sitosterol at higher temperatures. This indicates the feasibility of having an organogelling agent in dynamic exchange between solid and liquid phase, which is an essential feature of triglyceride networks.

Modeling gas solubilities in imidazolium based ionic liquids with the [Tf2N] anion using the GC-EoS

The group contribution equation of state (GC-EoS) is extended to model gas solubilities in the homologous 1-alkyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide family. The gases considered in this work are CO2, CO, H2, CH4, and C2H6. The model parameters were estimated on the basis of 1400 experimental data points in the temperature range of 278–460 K and pressures up to 160 bars. A correlation is also presented to calculate the critical diameter, a characteristic parameter of the GC-EoS repulsive term, as a function of the ionic liquid molar volume. Density data is most often available for ionic liquids; hence, the correlation provides a predictive method for ionic liquids not included in the parameterization process. The new parameters were then used to predict the phase behavior of binary mixtures containing different solutes (including C3H8, C4H10, and C6H14) and ionic liquids with different chain lengths than those used in the parameterization process.

Orientational ordering and phase behaviour of binary mixtures of hard spheres and hard spherocylinders.

We study the structure and fluid-phase behaviour of binary mixtures of hard spheres (HSs) and hard spherocylinders (HSCs) in isotropic and nematic states using the NPnAT ensemble Monte Carlo (MC) approach in which the normal component of the pressure tensor is fixed in a system confined between two hard walls. The method allows one to estimate the location of the isotropic-nematic phase transition and to observe the asymmetry in the composition between the coexisting phases, with the expected enhancement of the HSC concentration in the nematic phase. This is in stark contrast with the previously reported MC simulations where a conventional isotropic NPT ensemble was used. We further compare the simulation results with the theoretical predictions of two analytic theories that extend the original Parsons-Lee theory using the one-fluid and the many-fluid approximations [Malijevský et al., J. Chem. Phys. 129, 144504 (2008)]. In the one-fluid version of the theory, the properties of the mixture are related to an effective one-component HS system, while in the many-fluid theory, the components of the mixtures are represented as separate effective HS particles. The comparison reveals that both the one- and the many-fluid approaches provide a reasonably accurate quantitative description of the mixture including the predictions of the isotropic-nematic phase boundary and degree of orientational order of the HSC-HS mixture.

Phase Behavior of Binary Mixtures of a Liquid Crystal and Methane

Phase diagrams of binary systems of four different liquid crystals with different polarity and CH4 are investigated experimentally in this study. The solubility of CH4 in liquid crystals has not been studied before. The liquid crystals used were 4-ethyl-4′-propylbicyclohexyl, 4-pentylcyclohexyl-4′-benzonitrile, 4-pentyl-4′-cyanobiphenyl, and 4-pentyloxy-4′-cyanobiphenyl. The concentration of the methane used was 0.01 wt %. The phase diagrams were studied in the temperature range of (295 to 365) K and up to 13 MPa. The phase equilibria studied were the three-phase equilibria nematic + isotropic + gas, smectic + isotropic + gas, and the two-phase equilibria isotropic + gas ↔ isotropic, nematic + isotropic ↔ isotropic, nematic ↔ nematic + isotropic, and smectic + isotropic ↔ isotropic. The main conclusion of this study is that increasing the polarity of the solvent leads to a lower solubility of CH4.

Phase behavior of binary mixture systems of saturated-unsaturated mixed-acid triacylglycerols: effects of glycerol structures and chain-chain interactions.

We systematically examined the phase behavior of binary mixtures of mixed-acid triacylglycerols (TAGs) containing palmitic and oleic acid moieties 1,3-dioleoyl-2-palmitoyl-glycerol (OPO), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO), and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), which are widely present in natural fats and are employed in the food, pharmaceutical, and cosmetic industries. Differential scanning calorimetry and X-ray diffraction methods were applied to observe the mixing behavior of PPO/OPO, OOP/OPO, and PPO/OOP under metastable and stable conditions. The results led to three conclusions: (1) Eutectic behavior was observed in PPO/OPO. (2) Molecular compound (MC) crystals were formed in the mixtures of OOP/OPO and PPO/OOP. (3) However, the MC crystals occurred only under metastable conditions and tended to separate into component TAGs to form eutectic mixture systems after 17 months of incubation. These results were contrary to those of previous studies on 1,3-dipalmitoyl-2-oleoyl glycerol (POP)/OPO and POP/PPO in which the MC crystals were thermodynamically stable. We determined that specific molecular interactions may cause this different phase behavior (stability of POP/OPO and POP/PPO MC crystals and metastability of OOP/OPO and PPO/OOP MC crystals). All results confirm the significant effects of molecular structures of glycerol groups, interactions of fatty acid chains, and polymorphism of the component TAGs on the mixing behavior of mixed-acid TAGs.

Application of a group contribution equation of state to model the phase behavior of mixtures containing alkanes and ionic liquids

In this work, the group contribution equation of state (GC-EoS) of Skjold-Jørgensen was used to model the phase behavior of mixtures of alkanes with different members of the homologous family 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [x-Mpyr][NTf2] ionic liquids. Pure group parameters for the ionic liquid functional group (MpyrNTf2) and interaction parameters between this group and the paraffin main group (sub-groups CH3 and CH2) were obtained from activity coefficients at infinite dilution found in literature for binary mixture {alkane+[x-Mpyr][NTf2] ionic liquid}. The GC-EoS of Skjold-Jørgensen, extended with these new parameters, was applied to predict with satisfactory results the phase behavior of binary mixtures {alkane+ [x-Mpyr][NTf2]}. In order to evaluate the GC-EoS performance in the prediction of liquid–liquid equilibria (LLE), experimental LLE data for binary mixtures {hexane, or heptane, or octane, or nonane, or decane +1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMpyr][NTf2]} were determined from T=(293.15 to 333.15)K

Self-assembly of imidazolium-based surfactants in magnetic room-temperature ionic liquids: binary mixtures.

The phase behaviour of binary mixtures of ionic surfactants (1-alkyl-3-imidazolium chloride, C(n)mimCl with n=14, 16 and 18) and imidazolium-based ionic liquids (1-alkyl-3-methylimidazolium tetrachloroferrate, C(n)mimFeCl4, with n=2 and 4) over a broad temperature range and the complete range of compositions is described. By using many complementary methods including differential scanning calorimetry (DSC), polarised microscopy, small-angle neutron and X-ray scattering (SANS/SAXS), and surface tension, the ability of this model system to support self-assembly is described quantitatively and this behaviour is compared with common water systems. The existence of micelles swollen by the solvent can be deduced from SANS experiments and represent a possible model for aggregates, which has barely been considered for ionic-liquid systems until now, and can be ascribed to the rather low solvophobicity of the surfactants. Our investigation shows that, in general, C(n)mimCl is a rather weak amphiphile in these ionic liquids. The amphiphilic strength increases systematically with the length of the alkyl chain, as seen from the phase behaviour, the critical micelle concentration, and also the level of definition of the aggregates formed.

Phase behaviors of binary mixtures composed of banana-shaped and calamitic mesogens

In this work, five mixtures with different concentrations of banana-shaped and calamitic compounds have been prepared and subsequently studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction on non-oriented samples. The phase sequences and molecular parameters of the binary systems are presented.

Formation of Inverse Topology Lyotropic Phases in Dioleoylphosphatidylcholine/Oleic Acid and Dioleoylphosphatidylethanolamine/Oleic Acid Binary Mixtures

The addition of saturated fatty acids (FA) to phosphatidylcholine lipids (PC) that have saturated acyl chains has been shown to promote the formation of lyotropic liquid-crystalline phases with negative mean curvature. PC/FA mixtures may exhibit inverse bicontinuous cubic phases (Im3m, Pn3m) or inverse topology hexagonal phases (HII), depending on the length of the acyl chains/fatty acid. Here we report a detailed study of the phase behavior of binary mixtures of dioleoylphosphatidylcholine (DOPC)/oleic acid (OA) and dioleoylphosphatidylethanolamine (DOPE)/oleic acid at limiting hydration, constructed using small-angle X-ray diffraction (SAXD) data. The phase diagrams of both systems show a succession of phases with increasing negative mean curvature with increasing OA content. At high OA concentrations, we have observed the occurrence of an inverse micellar Fd3m phase in both systems. Hitherto, this phase had not been reported for phosphatidylethanolamine/fatty acid mixtures, and as such it highlights an additional route through which fatty acids may increase the propensity of bilayer lipid membranes to curve. We also propose a method that uses the temperature dependence of the lattice parameters of the HII phases to estimate the spontaneous radii of curvature (R0) of the binary mixtures and of the component lipids. Using this method, we calculated the R0 values of the complexes comprising one phospholipid molecule and two fatty acid molecules, which have been postulated to drive the formation of inverse phases in PL/FA mixtures. These are -1.8 nm (±0.4 nm) for DOPC(OA)2 and -1.1 nm (±0.1 nm) for DOPE(OA)2. R0 values estimated in this way allow the quantification of the contribution that different lipid species make to membrane curvature elastic properties and hence of their effect on the function of membrane-bound proteins.

Phase behavior of binary mixture for the isoalkyl acetate in supercritical carbon dioxide

Pressure–composition isotherms of phase equilibria for the CO2+isoalkyl acetate systems are investigated in the static method at five temperatures of (313.2, 333.2, 353.2, 373.2 and 393.2)K and pressures up to 18.24MPa. The CO2+isobutyl acetate, CO2+isopentyl acetate and CO2+isooctyl acetate systems have continuous critical mixture (locus) curves that exhibit maximums in pressure–temperature space between the critical temperatures of CO2 and isoalkyl acetate (isobutyl acetate, isopentyl acetate and isooctyl acetate). The solubility of isobutyl acetate, isopentyl acetate and isooctyl acetate for the CO2+isobutyl acetate, CO2+isopentyl acetate and CO2+isooctyl acetate systems increases as the temperature increases at constant pressure. The CO2+isobutyl acetate, CO2+isopentyl acetate and CO2+isooctyl acetate systems exhibit type-I phase behavior. The experimental results for the CO2+isobutyl acetate, CO2+isopentyl acetate and CO2+isooctyl acetate systems are correlated with Peng–Robinson equation of state using a mixing rule including two adjustable parameters.