Liquid Phase Behavior Research Articles

Liquid crystal phase behavior of oxalated cellulose nanocrystal and optical films with controllable structural color induced by centripetal force

Cellulose nanocrystal (CNC) is a sustainable bio-nanomaterial. The distinctive left-handed polarization properties render cellulose nanocrystal a promising candidate for optical film. Due to eco-friendliness, reliability, mildness and simplicity, the oxalate hydrolysis method stands out among various preparation methods for CNC. This study delved into the liquid crystal phase behavior of oxalated cellulose nanocrystal derived from pulp, and discovered the influences of CNC concentration and pH on suspension stability and phase transition, and evaluated its optical properties. The results demonstrated that oxalated CNC presented two different liquid crystal phases, the nematic phase and the cholesteric phase. The stability mechanism of CNC suspension and the regulatory principle of the liquid crystal phase transition were revealed. A novel CNC film-forming technology, the multilayer spin-coating technique, was developed for cellulose nanocrystal optical films. Driven by centrifugal force, cellulose nanocrystals were induced to self-assembly and formed the optical film with circular dichroism and structural color. This simple and efficient film-forming technology promised rapid processing (1 h) and controllable film structure and optical properties compared to traditional technologies. This work provided a theoretical understanding and practical prospects for integrating oxalated cellulose nanocrystal into sustainable advanced optical film materials.

Multiphase Behavior of the Water + 1-Butanol + Deep Eutectic Solvent Systems at 101.3 kPa

The growing demand for more sustainable routes and processes in the mixture separation and purification industry has generated a need to search for innovations, with new solvent alternatives being a possible solution. In this context, a new class of green solvents, known as deep eutectic solvents (DESs), has been gaining prominence in recent years in both academic and industrial spheres. These solvents, when compared to ionic liquids (ILs), are more environmentally friendly, less toxic, low-cost, and easier to synthesize. In addition, they have significantly lower melting points than their precursors, offering a promising option for various applications in this industrial sector. Understanding and studying the thermodynamic behavior of systems composed of these substances in purification and separation processes, such as liquid–liquid extraction and azeotropic distillation, is extremely important. This work aimed to study the phase behavior of liquid–liquid equilibrium (LLE) and vapor–liquid equilibrium (VLE) of water + 1-butanol + DES (choline chloride + glycerol) systems with a molar ratio of 1:2. Experimental LLE data, obtained at 298.15 K and 101.3 kPa, and VLE data, obtained at 101.3 kPa and in the temperature range of 364.05 K–373.85 K, were submitted to the thermodynamic quality/consistency test, proposed by Marcilla et al. and Wisniak, and subsequently modeled using the gamma–gamma approach for the LLE and gamma–phi for the VLE. The non-random two-liquid (NRTL) model was used to calculate the activity coefficient. The results are presented for the VLE in a temperature–composition phase diagram (triangular prism) and triangular phase diagrams showing the binodal curve and tie lines (LLE). The separation and distribution coefficients of LLE were determined to evaluate the extractive potential of the DES. For the VLE, the values of the relative volatility of the system were calculated, considering the entrainer free-basis, to evaluate the presence or absence of azeotropes in the range of collected points. From these data, it was possible to compare DES with ILs as extracting agents, using data from previous studies carried out by the research group. Therefore, the results indicate that the NRTL model is efficient at correlating the fluid behavior of both equilibria. Thus, this study serves as a basis for future studies related to the understanding and design of separation processes.

Chiral hydroxypropyl cellulose and nanocellulose liquid crystal structural and phase behavior elucidation and their photonic elastomer advanced manufacturing – A Review

Chiral hydroxypropyl cellulose and nanocellulose liquid crystal structural and phase behavior elucidation and their photonic elastomer advanced manufacturing – A Review

Zwitterionic and vinyl-N-imidazolium ionic liquids

In this paper, we present employing our own and literature data the results of investigation of the thermal behavior and ion transport properties of vinyl and alkyl imidazolium zwitterions containing an alkane sulfonic acid group and salts on their basis. For comparison, we present the results of investigation the respective vinyl and alkyl imidazolium ILs without these functional groups. The phase behavior of zwitterionic and vinyl imidazolium ionic liquids is studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Organic template-free synthesis of CHA zeolite by hydrothermal conversion of magadiite with the assistance of seeds and an investigation of crystallization mechanism

This study aims to explore the process of pure CHA zeolite production by a hydrothermal magadiite transformation method, with the chemical formulation of 36 NaOH: 40 SiO2: Al2O3: 400H2O, running for 7 h at 80 °C with 12 wt% seeds. Considering various synthesis factors such as NaOH/SiO2, temperature, and seeds dosage etc., XRD, SEM, FT-IR, Solid-state MAS NMR and ESI-MS were applied to investigated to discuss the transformation behavior and mechanism in both solid and liquid phase. The results indicated that the changes of secondary building units had a formation sequence progresses from 6 R s to D6Rs, and oligomers in liquid phases would take part in the formation of CHA framework. In conclusion, the study demonstrates a novel pathway for the highly efficient and green synthesis of CHA zeolite via seed-assisted hydrothermal conversion of magadiite.

Liquid-liquid equilibrium of the 1-butyl-3-methylimidazolium-based ionic liquids + sodium citrate + water systems at 298.15 K

Liquid-liquid extraction has long been the preferred option for process engineers to develop separation processes and it is used to separate and purify various biological products, metallic ions, colorants, pharmaceutical molecules, and small organic species. Ionic liquids (ILs) are special ecological solvents that can be used as possible substitutes for traditional organic solvents used for extraction and separation processes, becoming them more sustainable and safer. In combination with salts or inorganic polymers, they can form a liquid system of two phases, advantageous due to its wide polarity and viscosity. In this scenario, liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems containing ionic liquid ([BMIM][OH], [BMIM][Cl], [BMIM][Br]) (1) + sodium citrate (2) + water (3) were determined experimentally at 298.15 K. The ionic liquids were synthesized and characterized in the first part of the study. COSMO-RS was used as a tool to calculate polarity graphs of study molecules. In the second part, liquid–liquid equilibrium was studied using experimental measurements of the binodal curve and tie-lines, testing the quality of experimental data by mass balance, thermodynamic modeling using the NRTL model to correlate liquid–liquid equilibrium data and to do their phase stability. The accuracy of the model data results was verified by Gibbs energy topological mixing surface analysis and σ profiles. The experimental results indicated that the studied systems had type I liquid–liquid phase behavior. It was demonstrated that the ionic liquid [BMIM][OH] demonstrated better behavior to form Aqueous Two-Phase Systems mixed with sodium citrate and water. The results obtained by the thermodynamic modeling and stability with NRTL model weren’t satisfactory, because, besides the low deviations for the liquid phases compositions, the majority of calculated tie-lines was not tangent with the Gibbs surface, showing the limitations of the model for systems with electrolytes.

Influence of minor Mg/Ca/Nb/Ag addition on the morphology and microstructure of Fe-rich phase in powder metallurgy Cu[sbnd]10Fe alloy

The effect of Mg/Ca/Nb/Ag alloying on the morphology and microstructure of powder metallurgy Cu10Fe alloy was investigated systemically in this work. Alloying of Ca reduces the size of Fe-rich particles, while alloying of Mg/Nb/Ag increases the Fe-rich particles. This is attributed to the different roles of various alloying elements on the liquid-phase separation behaviors as well as diffusion of Fe atoms during the solidification. Coarse size spherical Fe-rich particles with a face centered cubic structure are observed in CuFe alloys bearing Mg/Ag/Nb, whilst the alloying of Ca favors the formation of fine spherical Fe-rich particles with a body centered cubic structure. The factor governing the morphology is found to be interfacial energy for CuFe alloys containing Mg/Ag/Nb and elastic energy for Cu-Fe-Ca alloy, respectively. Coarse size Fe-rich particles are hard to deform during subsequent rolling, but the fine Fe-rich particles can co-deform with Cu matrix. This study could provide a detailed picture regarding the influence of various alloying element types on the size, morphology, and lattice structure of Fe phase of CuFe alloy.

Low-temperature and high-pressure phase transitions of ionic liquid 1-decyl-3-methylimidazolium bromide

The phase behavior of an ionic liquid (IL) was investigated at low temperature (LT) and high pressure (HP). The utilized IL was 1-decyl-3-methylimidazolium bromide ([C10mim][Br]), whose cation possesses a long alkyl side-chain. The LT- and HP-crystal polymorphs of [C10mim][Br] were observed conducting small- and wide-angle X-ray scattering (SWAXS) experiments. Upon cooling, a liquid crystal was formed, which subsequently transformed into crystalline species with the modulated layered structure possessing the double Bragg reflection. In addition to the layered structure, the hybrid layered structure coexisted upon heating. At HP, 00ℓ Bragg reflections representing the layered structure were not observed in SWAXS patterns. The HP-crystal phase of [C10mim][Br] was characterized by double Bragg reflection in the low scattering wavevector region. The non-layered HP-crystal caused the large bulk modulus.

Phase diagram of a rigid rod system with attractive end groups

We present a molecular dynamics study into the thermotropic liquid crystalline phase behaviour of a coarse-grained model of a rigid bolaamphiphilic molecule. The model consists of 11 spherical beads held in a fixed linear arrangement, where the two opposing terminal beads are self-attracting, mimicking hydrophilic segments and the remaining internal beads, as well as cross-bead interactions, are softly repulsive, mimicking hydrophobic organic segments. The effect of the model’s end bead self-attraction strength on liquid crystalline phase behaviour is studied. Coexistence points between the smectic A, nematic and isotropic phases exhibited by the model are determined following a thermodynamic integration pathway, using equations of state constructed by multiple histogram reweighting of simulation data. Variants of Gibbs–Duhem integration are used to trace pressure–temperature coexistence curves. Under isobaric conditions, the effect of increasing the end-group self-attraction on the nematic–isotropic coexistence temperature is relatively small; however, the nematic phase stability is reduced at the expense of a significant increase in the smectic A–nematic coexistence temperature. Lower temperature simulations show the approximate smectic A–crystalline transition temperature to be only weakly dependent on the strength of the end-group self-attraction.

Active crystallization from power functional theory.

We address the gas, liquid, and crystal phase behaviors of active Brownian particles in three dimensions. The nonequilibrium force balance at coexistence leads to equality of state functions for which we use power functional approximations. Motility-induced phase separation starts at a critical point and quickly becomes metastable against active freezing for Péclet numbers above a nonequilibrium triple point. The mean swim speed acts as a state variable, similar to the density of depletion agents in colloidal demixing. We obtain agreement with recent simulation results and correctly predict the strength of particle number fluctuations in active fluids.

Complex phase behavior of dihydroxyl-functionalized ionic liquids at low temperature.

Here, we have synthesized six dihydroxyl-functionalized ionic liquids for phase behavior studies at low temperature via crystallographic methods, Raman spectroscopy, differential scanning calorimetry (DSC), and density functional theory (DFT) calculations. Phase varieties are observed depending on the direction and strength of hydrogen bonding. Our studies also show that the ILs could be potentially excellent phase-change thermal storage materials with nearly no change of the phase transition enthalpy.

Tuning the low-temperature phase behavior of aqueous ionic liquids.

Water's anomalous behavior is often explained using a two-liquid model, where two types of water, high-density liquid (HDL) and low-density liquid (LDL), can be separated via a liquid-liquid phase transition (LLPT) at low temperature. Mixtures of water and the ionic liquid hydrazinium trifluoroacetate were suggested to also show an LLPT but with the advantage that there is no rapid ice crystallization hampering its observation. It remains controversial whether these solutions exhibit an LLPT or are instead associated with complex phase separation phenomena. We here show detailed low-temperature calorimetry and diffraction experiments on aqueous solutions containing hydrazinium trifluoroacetate and other similar ionic liquids, all at a solute mole fraction of x = 0.175. Hydrazinium trifluoroacetate, ammonium trifluoroacetate, ethylammonium trifluoroacetate and hydrazinium pentafluoropropionate all boast exothermic transitions unrelated to crystallization as well as remarkable structural changes upon cooling into the glassy state. We propose a model inspired by micelle formation and decomposition in surfactant solutions, which is complemented by MD simulations and allows rationalizing the rich phase behavior of our mixtures during cooling. The fundamental aspect of the model is the hydrophobic nature of fluorinated anions that enables aggregation, which is reversed upon cooling and culminates in the remarkable exothermic first-order transition observed at low temperature. That is, we assign the first-order transition not to an LLPT but to phase-separations similar to the ones when falling below the Krafft temperature. All other solutions merely show simple vitrification behavior. Still, they exhibit distinct differences in liquid fragility, which is decreased continuously with decreasing hydrophobicity of the anions. This might enable the systematic tuning of ionic liquids with the goal of designing aqueous solutions of specific fragility.

Ternary Mixtures of Hard Spheres and Their Multiple Separated Phases

We study the liquid phase behavior of ternary mixtures of monodisperse hard spheres in solution. The interactions are modeled in terms of the second virial coefficient and can be additive hard sphere (HS) or non-additive hard sphere (NAHS) interactions. We give the set of equations that defines the phase diagram for mixtures of three components. We calculate the theoretical liquid–liquid phase separation boundary for two-phase separation (the binodal) and, if applicable, the three-phase boundary, as well as the plait points and the spinodal. The sizes of the three components are fixed. The first component (A) is the smallest one, the second component (B) is four times the size of the smallest component, and the third (C) component is three times the size of the smallest one. The interaction between the first two components is fixed, and this AB sub-mixture shows phase separation. The interactions of component C with the other two components are varied. Component C can be compatible or incompatible with components A and B. Depending on the compatibility of the components, the phase diagram is altered. The addition of the third component has an influence on the phase boundary, plait points, stability region, fractionation, and volume ratio between the different phases. When all sub-mixtures (AB, AC, and BC) show phase separation, a three-phase system becomes possible when the incompatibility among all components is high enough. The position and size of the three-phase region is dependent on the interactions between the different sub-mixtures. We study the fractionation off all components depending on specific parent concentrations.

VLE measurement of binary systems 1-butyl-3-methylimidazolium-based ionic liquids and ethanol or water

Experimental vapor–liquid equilibrium (VLE) data for binary systems of ethanol or water with four ionic liquids (ILs) comprising 1-butyl-3-methylimidazolium cation and different anions were measured at atmospheric pressure within a broad region of IL concentrations, IL mole fraction ranging between 0 and 0.7 or even 0.87. Siwoloboff procedure of vapor–liquid phase transition temperature measurement was applied to estimate VLE of the binary mixtures. Obtained t–x data were fitted assuming ideal vapor and non-ideal liquid phase behavior, using the original NRTL equation to calculate component activity coefficients. VLE description results are presented in form of equilibrium diagrams and as the variation of activity coefficients with mixture composition. Quality of the VLE data fitting was assessed based on root mean square deviations and mean deviations in temperature. Some experimental binary t–x data sets were compared to those available in literature (measured in much narrower concentration range) or predicted from ternary VLE data. The selection of ILs in this study was related to the separation of ethanol−water mixture by extractive distillation. Principal IL selection criterium was its ability to affect the ethanol–water relative volatility. Thermodynamic description of the VLE data of IL-containing systems within a wide concentration range is an essential building block of the mathematical model of separation devices, especially in case of regeneration equipment where concentrated IL is present.

Phase behaviour and aggregate structures of the surface-active ionic liquid [BMIm][AOT] in water

HypothesisThe surface-active ionic liquid, 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate ([BMIm][AOT]), has a sponge-like bulk nanostructure consisting of percolating polar and apolar domains formed by the ion charge groups and alkyl chains, respectively. We hypothesise that added water will swell the polar domains and change the liquid nanostructure. ExperimentsSmall angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and polarizing optical microscopy (POM) were used to investigate the nanostructure of [BMIm][AOT] as a function of water content. Differential scanning calorimetry (DSC) was employed to probe the thermal transitions of [BMIm][AOT]-water mixtures and the mobility of water molecules. FindingsSAXS, SANS and POM show that at lower water contents, [BMIm][AOT]-water mixtures have a sponge-like nanostructure similar to the pure SAIL, at medium water contents a lamellar phase forms, and at high water contents vesicles form. DSC results reveal that water molecules are supercooled in the lamellar phase. For the first time, results reveal a series of transitions from inverse sponge, to lamellar then to vesicles, for [BMIm][AOT] upon dilution with water.

Mott‐Limited Thermopower of Pascal Electron Liquid Phases at the LaAlO3/SrTiO3 Interface

The cover image shows the signature conductance behavior of the Pascal electron liquid phase, observed in LaAlO3/SrTiO3 electron waveguides. The thermoelectric properties of this system are defined by the existence of electronic states in which bound states of n = 2, 3, 4,… electrons contribute to transport, and provide unique insight into this remarkable state of matter. For further details, see article number 2200612 by Jeremy Levy and co-workers.

Influence of imidazolium based ionic liquids with different anions on liquid–liquid phase behavior for separation of azeotropic mixture isopropyl alcohol + diisopropyl ether

During production of isopropyl alcohol (IPA) by propylene hydration, a mixture of diisopropyl ether (DIPE) and IPA is obtained as a byproduct. Because DIPE and IPA have similar boiling points, an azeotrope can be formed. It is not feasible to separate the mixture (DIPE + IPA) using conventional distillation technology. In this work, the mixture (DIPE + IPA) was separated by liquid–liquid extraction and three imidazolium based ionic liquids (ILs) with different anions including 1-butyl-3-methylimidazolium thiocyanate ([BMIM]SCN), 1-butyl-3-methylimidazolium dicyanamide ([BMIM]DCA) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]NTf2) were selected as the extractants. The effect of the ILs on liquid–liquid phase behavior for the ternary systems (DIPE + IPA + ILs) was discussed. Partition ratio (P) and selectivity (S) were calculated to assess the extraction ability of the ILs. The NRTL thermodynamic model was used to correlate the experimental data. The interactions between the ILs and (DIPE / IPA) were explored by analyzing electrostatic potentials, hydrogen bond length and reduced density gradient, which can help to design the ILs with reasonable structures for separating such azeotropic mixtures.

Investigation of Nonidealities through an Extended Flory–Huggins Model of Ionic Liquid Mixtures with Ammonia

The phase behavior of ionic liquids and ammonia is critical due to their application in various fields such as sorption-based heating/cooling cycles and direct ammonia capture. To date, various ionic liquids have been developed and investigated to enhance the solubility of ammonia without compromising the reversibility due to recycling concerns and various thermodynamic models have been used to correlate the experimental vapor–liquid equilibria data. Surely, high ammonia sorption capacities are required and understanding the interaction between ammonia and ionic liquids can lead to synthesizing targeted ionic liquids for ammonia. In this study, we developed an extended Flory–Huggins model on ammonia and imidazolium-based ionic liquid systems, where both combinatorial and residual terms are considered, to understand the interaction between ammonia and ionic liquids. The results showed that the nonidealities in ammonia and imidazolium-based IL mixtures are due to both entropic and enthalpic contributions. Therefore, increasing the size of the IL would not be enough to achieve higher solubilities. A deeper understanding of the molecular-level interaction between ionic liquids and ammonia can be investigated via molecular simulations.

Bis cinnamate substituted λ-shaped azo liquid crystal: effect of molecular structure on mesomorphic properties

A new class of λ-shaped azo materials with a cinnamate linkage group has been designed, synthesized, and well-characterized. Further, the liquid crystalline property has been studied by using POM and DSC analysis. Out of six derivatives, five compounds displayed liquid crystalline properties. The liquid crystalline property is observed in an enantiotropic manner. The structure–property relationship is further studied for the understanding of the exhibition of liquid crystalline properties. The results showed that their liquid crystalline phase behavior was closely related to the number of mesogenic units, rigidity, and flexibility of the molecular systems.

Toward high-performance associative extraction by forming deep eutectic solvent: A component pairing and mechanism study

Associative extraction by selectively forming deep eutectic solvent (DES) with the target solute exhibits high performance toward many hard-to-separate systems; however, selecting a proper associative extractant for a specific task is challenging as high extraction efficiency and forming liquid DES should be satisfied simultaneously. In this work, a systematic component pairing method is proposed to rationally select suitable hydrogen bond acceptors (HBA) for associative extraction, which includes three steps: collecting HBA candidates, theoretical pairing from extraction potential evaluation and solid–liquid phase behavior estimation, and experimental validation. For two exemplary separation cases, (i.e., detergent range alcohol-alkane mixture and phenol-toluene mixture), suitable HBAs with high extraction performance and wide liquid operating window are successfully selected, demonstrating the reliability of the method. Hydrogen bonding interaction drives the selective formation of DES with the target solute, and the interaction strength depends on the solute structure, which in turn determines the selection of suitable HBAs.