Phase Behavior Of Mixtures Research Articles

Comparison of four different PC- SAFT versions to predict liquid-liquid equilibria of polymer and asphaltene systems at low temperatures

In this work, a simple temperature- and density-effective diameter expression recently published in the literature was combined with a new set of universal constants for the perturbed chain-statistical association fluid theory equation of state (PC- SAFT EoS). Then, the resulting PC- SAFT version was used to perform thermodynamic calculations of Brown's first- order ideal curves, phase behavior for simple hydrocarbon binary mixtures (critical loci), cloud-points (CP) for ternary polymeric mixtures, and asphaltene onset pressures (AOPs) for ill- and well-defined hydrocarbon mixtures prone to precipitate asphaltenes. In addition, the new PC- SAFT version was used to predict the crossover temperatures of one of the ill-defined petroleum mixtures under the injection of different amounts of CO2. This modified PC- SAFT model predicted both AOPs and CPs lower than those found by using the original universal constants by Gross and Sadowski (GS). The predictive calculations with both GS and Liang- Kontogeorgis (LK) universal constants produced as a result that a temperature- and density-dependent effective diameter significantly modifies the predictions for dense and complex systems, while does not generate an important impact on the calculation of properties of systems made-up by simple molecules under ordinary conditions.

Modulating the crystallization of phytosterols with monoglycerides in the binary mixture systems: mixing behavior and eutectic formation

Phytosterols (PSs) are insoluble in water and poorly soluble in oil, which hampers their potential as cholesterol level regulator in human. To mitigate this problem, monoglycerides (MGs) were used to modulates the crystallization behavior of PSs. Therefore, the understanding on mixing behavior provides the insight into different aspects of crystallization and the resultant effects. The effects on thermal, morphology, diffraction, and spectroscopy behavior were investigated for binary mixtures of 11 different ratios (100:0 to 0:100 MGs:PSs). The phase behavior of binary mixtures of commercial MGs and PSs exhibited complexity with the formation of eutectic mixtures at 90:10 and 80:20 (MGs:PSs) combinations. These combinations revealed a single melting profile and reduced melting enthalpy, though after a month of storage at 5 °C. Conversely, two separate melting regions were observed in others. Furthermore, powder X-ray diffraction (PXRD) analysis of selected combinations revealed a change in crystalline forms with changes in the peaks located between 18-19° (2θ) and 25-26° (2θ). Accordingly, Raman spectroscopy results revealed changes in intensities and peak shape. Therefore, the change in crystalline forms or behavior correlated well to the change in thermal properties. Overall, the characterizations revealed the formation of eutectic mixtures between MGs and PSs at 90:10 and 80:20 (MGs:PSs) in which MGs modified the crystallization of PSs and changed the crystal forms thus, thermal behaviors. This study provides new insight into the mixing behavior of MGs and PSs which supports other research. Therefore, the results of this study are beneficial for the improvement of formulation of phytosterols in food and pharmaceutical products. Nonetheless, this study reveals a simple technique to alter crystal forms of phytosterols through simple complexation with monoglycerides.

Global phase diagrams in a polymer-solvent system under the positive and negative pressure at and near the mathematical double points

Global phase diagrams are one of the crucial tools to investigate the phase behavior of simple and complex mixtures both theoretically and experimentally. The critical lines and global phase behavior of polymer-solvent systems under the negative pressure at and near the mathematical double points (MDPs) are studied. We present the critical lines of polymer mixtures in three different planes for various values of interaction energy parameters, and change the factor (r) and the deviation coefficient (Δ) from the MDPs. We use the full Tompa model to obtain the equation for the critical line within the molecular-field approximation. We find that r and Δ values influence the critical lines and global phase behavior of the system. Moreover, as the r increases, the MDPs shift to the low-pressure region and it will be located in a negative pressure region forr≥9.

Predicting the phase behavior of mixtures of active spherical particles.

An important question in the field of active matter is whether or not it is possible to predict the phase behavior of these systems. Here, we study the phase coexistence of binary mixtures of torque-free active Brownian particles for both systems with purely repulsive interactions and systems with attractions. Using Brownian dynamics simulations, we show that phase coexistences can be predicted quantitatively for these systems by measuring the pressure and "reservoir densities." Specifically, in agreement with the previous literature, we find that the coexisting phases are in mechanical equilibrium, i.e., the two phases have the same pressure. Importantly, we also demonstrate that the coexisting phases are in chemical equilibrium by bringing each phase into contact with particle reservoirs and show that for each species, these reservoirs are characterized by the same density for both phases. Using this requirement of mechanical and chemical equilibrium, we accurately construct the phase boundaries from properties that can be measured purely from the individual coexisting phases. This result highlights that torque-free active Brownian systems follow simple coexistence rules, thus shedding new light on their thermodynamics.

Influence of Carboxylate Anions on Phase Behavior of Choline Ionic Liquid Mixtures.

Mixing ionic liquids is a suitable strategy to tailor properties, e.g., to reduce melting points. The present study aims to widen the application range of low-toxic choline-based ionic liquids by studying eight binary phase diagrams of six different choline carboxylates. Five of them show eutectic points with melting points dropping by 13 to 45 °C. The eutectic mixtures of choline acetate and choline 2-methylbutarate were found to melt at 45 °C, which represents a remarkable melting point depression compared to the pure compounds with melting points of 81 (choline acetate) and 90 °C (choline 2-methylbutarate), respectively. Besides melting points, the thermal stabilities of the choline salt mixtures were investigated to define the thermal operation range for potential practical applications of these mixtures. Typical decomposition temperatures were found between 165 and 207 °C, with choline lactate exhibiting the highest thermal stability.

Saddle-splay-induced periodic edge undulations in smectic-A disks immersed in a nematic medium.

We report experimental studies on the phase behavior of binary mixtures of 1″,7″-bis(4-cyanobiphenyl-4'-yl)heptane (CB7CB) and 4,4-diheptyloxyazoxybenzene, which exhibit, apart from the nematic (N) and twist-bend nematic (N_{TB}) phases, the induced smectic-A (Sm-A) phase for weight fraction of CB7CB between 0.05 and 0.70. In planar nematic layers, the N_{TB} phase separates as droplets of tactoidlike planform; the chirality of droplets manifests in the optical dissimilarity between their opposite angular ends. Our main result is that, in the appropriate two phase region, Sm-A nuclei with positive dielectric anisotropy change over to disks immersed in the nematic above some electric field, their edges decorated by periodic bright spots, a result which was earlier reported in another binary system exhibiting the induced Sm-A phase [R. Pratibha and N. V. Madhusudana, Physica A 224, 9 (1996)10.1016/0378-4371(95)00311-8]. We develop a simple theory for the threshold of this distortion, which is a periodic undulation of the edge of the disk, demonstrating that it arises from saddle-splay elasticity of Sm-A, the low Sm-A-N interfacial tension unable to suppress the distortion. The observed increases in the number of bright spots with field, and with the radius of the disk at a given field, in both the experimental systems are also accounted for by the model. The distortion, which results in the most direct visualization of saddle splay in Sm-A, is also exhibited by disks nucleating on surfaces treated for homeotropic anchoring.

Expanding the Solubility Parameter Method MOSCED to Pyridinium-, Quinolinium-, Pyrrolidinium-, Piperidinium-, Bicyclic-, Morpholinium-, Ammonium-, Phosphonium-, and Sulfonium-Based Ionic Liquids.

MOSCED (modified separation of cohesive energy density) is a solubility parameter method that offers an improved treatment of association interactions. Solubility parameter methods are well known for their ability to both make quantitative predictions and offer a qualitative description of the underlying molecular-level driving forces, lending themselves to intuitive solvent selection and design. Currently, MOSCED parameters are available for 130 organic solvents, water, and 33 imidazolium-based room temperature ionic liquids (ILs). In this work, we expand MOSCED to cover 66 additional ILs containing the pyridinium, quinolinium, pyrrolidinium, piperidinium, bicyclic, morpholinium, ammonium, phosphonium, and sulfonium cations using 10,052 experimental limiting activity coefficients. The resulting parameters may readily be used to predict the phase behavior in mixtures involving ILs.

Phase behavior of mixtures involving glassy materials

Many glassy materials decompose at higher temperatures and do not have a critical state. This forces researchers who use equations of state (EOS) that require a critical state to create fictitious critical properties. Understanding the thermo-mechanical and physical properties as well as the phase behavior of these materials is extremely important in the successful design of devices, laminates and green solvents, in oil exploration, transportation and processing, etc.The approach proposed in this work uses the glass transition temperature for glassy components, instead a fictitious critical state, within the multi-scale Gibbs-Helmholtz Constrained (GHC) cubic EOS framework to calculate thermo-physical properties and phase equilibrium. The approach is rigorous, self-consistent, and does not require model parameters to be regressed to experimental data. The main features of the proposed modeling framework for glassy materials are described and two examples of mixtures involving glassy materials are presented to elucidate key ideas.

Phase Behavior of Hydrocarbon Mixtures for the Low Concentration of Heavy Hydrocarbon Components

The present work shows the accurate calorimetric measurements of phase equilibria of hydrocarbon mixtures for the low concentration of heavy hydrocarbon components in particular the system methane + propane + decane with special emphasis on the concentration of decane below one mole percentage. Heat capacity, internal energy, pressure, and temperature derivative of pressure at constant volume for the ternary system have been measured in the range of 100–370 K and 0.1–40 MPa. To show a procedure of the phase diagram plotting by a precision adiabatic calorimetry, the typical phase diagram for a hydrocarbon mixture has been plotted in detail. A phase diagram has been plotted based on the experimental data of heat capacity, internal energy, pressure, and temperature derivative of pressure at constant volume. A phase transition is localized by a finite discontinuity in a temperature derivative of the thermodynamic potential. A closed area surrounded by the typical phase envelope for a pressure–temperature diagram is the two-phase region. Our particular attention is paid to the ternary system methane + propane + heavy hydrocarbon component for the low concentration of heavy hydrocarbon, in particular, of decane, due to the fact the conventional PVT approach does not guarantee the efficiency and accuracy of the phase diagram plotting for this system. Our investigations show the phase behavior of a hydrocarbon mixture for the low concentration of decane is drastically transformed compared to the customary concept. The hydrocarbon mixture splits into two phases, a macrophase enriched by methane and propane (a decane-poor phase) and a decane-rich microphase. To prove that all phases are equilibrium phases, a cooling mode of measurements is used. At the cooling mode of measurements, the same phase transitions as at the heating mode occur. These phase transitions correspond to the formation of a decane-rich microphase and a macrophase enriched by methane and propane.

Liquid–Liquid Phase Behavior of Solutions of 1,3-Diethylimidazolium Bis((trifluoromethyl)sulfonyl)amide in n-Alkyl Alcohols

The cloud point method is applied for the characterization of the limited miscibility of ionic liquid (IL) solutions. Here, we report the phase behavior of binary mixtures of the ionic liquid 1,3-d...

Fast understanding of phases and phase separation in liquid crystal drug delivery systems using deuterium solid-state NMR

Characterization of lipid based (SPC/GDO/H2O) liquid crystal (LC) drug delivery system is non-trivial and highly complex, especially when multiple and intermediate phases are present. The phase behavior of such mixtures during hydration or delivery is still poorly understood and therefore, characterizing these systems is crucially important towards controlling their function and enhancing the understanding of their drug release behavior. Current work has established an easy way to identify liquid crystal phases and phase mixtures using deuterium (2H) solid-state nuclear magnetic (NMR) spectroscopy under static conditions without disrupting the three dimensional structure and phases, as magic-angle spinning (MAS) could lead to disruption of the phases. Small angle X-ray scattering (SAXS) technique and optical microscopy were also employed to corroborate the study.

Effect of Tacticity on the Phase Behavior and Demixing of PαMSAN/dPMMA Blends Investigated by SANS

We investigate the effect of polymer tacticity on the phase behavior and phase separation of polymer mixtures by small-angle neutron scattering (SANS). Poly(α-methyl styrene-co-acrylonitrile) (PαMSAN) and deuterated poly(methyl methacrylate) (dPMMA) with two degrees of syndiotacticity were selected as a model partially miscible blend, as one of the most highly interacting systems known (defined by the temperature dependence of the blend’s interaction parameter). One-phase (equilibrium) and time-resolved, spinodal demixing experiments were analyzed by de Gennes’ random phase approximation (RPA) and Cahn–Hilliard–Cook (CHC) theory, respectively. The second derivative of the Gibbs free energy of mixing with respect to composition (G″ ≡ ∂2ΔGm/∂ϕ2) and corresponding χ parameter were obtained from both RPA and CHC analysis and found to correlate well across the phase boundary. We find that blends with higher PMMA syndiotacticity exhibit greater miscibility and a steeper G″ temperature dependence by ∼40%. The segment length of dPMMA with higher syndiotacticity was found to be a = 7.4 Å, slightly larger than 6.9 Å reported for lower syndiotacticity dPMMA. Consideration of thermal fluctuations is required for the self-consistent analysis of the nontrivial evolution of the spinodal peak position q* over time, corroborated by CHC model calculations. The temperature dependence of the mobility parameter, M, can be described by a “fast-mode” average of the diffusion coefficients of the blend constituents, except for quenches originating near the glass transition. A minimum demixing length scale of Λ ≈ 40 nm is obtained, in agreement with the theory for deeper quenches, but deviates at shallower quenches, whose origin we discuss. CHC correctly describes demixing length and time scales, except for quenches into the vicinity of the spinodal boundary. Our data demonstrate the significant effect of relatively minor polymer microstructure variations on polymer blend behavior across both sides of the phase boundary.

High-throughput morphology mapping of self-assembling ternary polymer blends.

Multicomponent blending is a convenient yet powerful approach to rationally control the material structure, morphology, and functional properties in solution-deposited films of block copolymers and other self-assembling nanomaterials. However, progress in understanding the structural and morphological dependencies on blend composition is hampered by the time and labor required to synthesize and characterize a large number of discrete samples. Here, we report a new method to systematically explore a wide composition space in ternary blends. Specifically, the blend composition space is divided into gradient segments deposited sequentially on a single wafer by a new gradient electrospray deposition tool, and characterized using high-throughput grazing-incidence small-angle X-ray scattering. This method is applied to the creation of a ternary morphology diagram for a cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) block copolymer blended with PS and PMMA homopolymers. Using “wet brush” homopolymers of very low molecular weight (∼1 kg mol−1), we identify well-demarcated composition regions comprising highly ordered cylinder, lamellae, and sphere morphologies, as well as a disordered phase at high homopolymer mass fractions. The exquisite granularity afforded by this approach also helps to uncover systematic dependencies among self-assembled morphology, topological grain size, and domain period as functions of homopolymer mass fraction and PS : PMMA ratio. These results highlight the significant advantages afforded by blending low molecular weight homopolymers for block copolymer self-assembly. Meanwhile, the high-throughput, combinatorial approach to investigating nanomaterial blends introduced here dramatically reduces the time required to explore complex process parameter spaces and is a natural complement to recent advances in autonomous X-ray characterization.

Phase Behavior of Binary Mixtures of Tripalmitin, Triolein, and Trilinolein

Phase Behavior of Binary Mixtures of Tripalmitin, Triolein, and Trilinolein

Phase diagrams of polymer-containing liquid mixtures with a theory-embedded neural network

We develop a deep neural network (DNN) that accounts for the phase behaviors of polymer-containing liquid mixtures. The key component in the DNN consists of a theory-embedded layer that captures the characteristic features of the phase behavior via coarse-grained mean-field theory and scaling laws and substantially enhances the accuracy of the DNN. Moreover, this layer enables us to reduce the size of the DNN for the phase diagrams of the mixtures. This study also presents the predictive power of the DNN for the phase behaviors of polymer solutions and salt-free and salt-doped diblock copolymer melts.

Monte Carlo simulations of patch models with applications to soft matter.

Patch models have been employed to describe anisotropic interactions in disparate soft matter systems. In this work, we present a unified study of a patch model to explore particle self-assembly in both monodisperse and polydisperse systems, with applications to both proteins and colloids. In the first case, we obtained a temperature-density phase diagram for a model of the protein polyglutamine from Monte Carlo simulations. These simulations evinced clusters in the gas phase and, via a comparison with the corresponding coarse-grained PLUM model for this system, we verified that dense clustering in the gas phase falls into the supersaturation region of the saturation curve. In the second case, we have investigated the effect of size polydispersity on the phase behavior of binary colloidal mixtures. It was found that the width of gas-liquid phase coexistence increases with increasing polydispersity and that, in addition to the aforementioned particle clustering, small particles decorate patches on large particles, thereby creating large-particle bridges. Our aim is to compare and contrast self-assembly in these two prototypical systems.

Clustering and phase separation in mixtures of dipolar and active particles.

The self-assembly of colloidal particles in dynamic environments has become an important field of study because of potential applications in fabricating out-of-equilibrium materials. We investigate the phase behavior of mixtures of passive dipolar colloids and active soft spheres using Brownian dynamics simulations in two dimensions. The phase behaviors exhibited include dipolar percolated network, dipolar string-fluid, isotropic fluid, and a phase-separated state. We find that the clustering of dipolar colloids is enhanced in the presence of slow-moving active particles compared to the clustering of dipolar particles mixed with passive particles. When the active particle motility is high, the chains of dipolar particles are either broken into short chains or pushed into dense clusters. Motility-induced phase separation into dense and dilute phases is also present. The area fraction of particles in the dilute phase increases as the fraction of active particles in the system decreases, while the area fraction of particles in the dense phase remains constant. Our findings are relevant to the development of reconfigurable self-assembled materials.

Phase Behavior for Crude Oil and Methane Mixtures: Crude Oil Property Comparison

A wide variation in composition and thermodynamic properties is expected for different reservoir fluids, from simplest one containing only methane and light compounds, to those with high compositional complexity. In this work, phase behavior of six different reservoir fluids recombined with methane was compared and contrasted. From our past work [Romero Yanes et. al. (2019), DOI:10.1016/j.fuel.2019.115850], a low asphaltene crude oil (28.0 °API, 0.68 wt % n-C7 asphaltenes), here referred as BRO, has presented a complex phase behavior when mixed with methane, especially when methane content is around 75.0 mol%. Based on these results, it was studied in this work the phase behavior of six different crude oil mixed with 75.0 mol% of methane. Samples main characteristics can be summarized as follows: a light condensate fluid (P1, 44.0 °API, and not detected n-C7 asphaltenes), three medium crude oils [(P2, 30.8 °API, and 0.09 wt % n-C7 asphaltenes); (P3, 26.0 °API, and 0.54 wt % n-C7 asphaltenes); and (P4, 25....

Phase behavior, thermodynamic and microstructure of concentrated pea protein isolate-pectin mixture: Effect of pH, biopolymer ratio and pectin charge density

The impact of pH, pea protein isolate (PPI)–pectin mixing ratio and pectin charge density on phase behavior (co-solubility, soluble complex and complex coacervates) of concentrated biopolymer mixture was investigated using state diagram and ζ–potential measurement. The microstructure, thermodynamic behavior, and non-covalent bonding of PPI to pectin were further explored by confocal laser scanning microscopy (CLSM), isothermal titration calorimetry (ITC), and Fourier transform infrared spectroscopy (FTIR). In general, the pH of soluble complex, complex coacervate formation shifted towards higher pH as PPI–pectin mixing ratio increased. Low methoxyl pectin (LMP) is favorable for complex coacervate over a wider pH range compared with high methoxyl pectin (HMP) due to its higher overall charge density. The CLSM images revealed that larger aggregates were formed in PPI-LMP coacervates. Both ITC and FTIR analyses indicated that soluble complex and complex coacervates were formed through the electrostatic interaction and hydrogen bonding between PPI and pectin.

P.570 Effects of ginseng and ginsenosides on mutant huntingtin aggregation, cellular apoptosis, mitochondrial dysfunction and motor impairment of Huntington's disease model

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.