Calculated Interaction Parameters Research Articles

Research on microscopic wetting mechanism of talcum powder by compounded surfactant for spraying dust reduction

Adding surfactant is an effective method to improve the dust removal efficiency of talcum powder dust. Based on the optimization of surfactants, this paper proposed an efficient compound surfactant scheme by calculating interaction parameters, adsorption simulation, and wettability test experiments. Molecular dynamics simulation was used to analyze the interaction mechanism between compound surfactant and talcum powder. Tests of spraying talcum powder with compound surfactants under different pressures were carried out. The results show that the combination of anionic surfactants SDS and SDBS with nonionic surfactants Tween 80 and AEO9 has a positive synergistic effect. The better the wetting effect of the compound system, the more ordered the surfactant molecules are arranged. Meanwhile, the diffusion ability of water molecules is stronger, and the thickness of the solid-liquid interface is larger. The wetting effect of compound surfactant on talcum powder is mainly influenced by van der Waals force. The dust removal efficiency test shows that SDS-Tween 80 compound surfactant with a pressure of 1.5 MPa and molar ratio of 0.4:0.6 is the best spray dust removal scheme. The research results are helpful to guide the application of compound surfactants in talcum powder dust control.

Thermoplastic polymers as water substitutes

Background. New applications of 3D printing have recently appeared in the fields of radiotherapy and radiology, but the knowledge of many radiological characteristics of the compounds involved is still limited. Therefore, studies are needed to improve our understanding about the transport and interaction of ionizing radiation in these materials. Purpose. The purpose of this study is to perform an analysis of the most important radiation interaction parameters in thermoplastic materials used in Fused Deposition Modeling 3D printing. Additionally, we propose improvements to bring their characteristics closer to those of water and use them as water substitutes in applications such as radiodiagnosis, external radiotherapy, and brachytherapy. Methods. We have calculated different magnitudes as mass linear attenuation, mass energy absorption coefficients, as well as stopping power and electronic density of several thermoplastic materials along with various compounds that have been used as water substitutes and in a new proposed blend. To perform these computations, we have used the XCOM and ESTAR databases from NIST and the EGSnrc code for Montecarlo simulations. Results. From the representation of the calculated interaction parameters, we have been able to establish relationships between their properties and the proportion of certain chemical elements. In addition, studying these same characteristics in different commercial solutions used as substitutes for water phantoms allows us to extrapolate improvements for these polymers. Conclusion. The radiological characteristics of the analyzed thermoplastic materials can be improved by adding some chemical elements with atomic numbers higher than oxygen and by using polyethylene in new blends.

Micellization, aggregation, interaction, and solubilization behaviors of mixed solutions of cationic gemini and nonionic surfactants

AbstractThe micellization properties of mixed aqueous solutions of a cationic gemini surfactant (CGS) and Triton X‐100, a conventional non‐ionic surfactant, with various mole fractions, were determined by measuring the surface tension at different temperatures. Various theoretical models were used to analyze the behavior of this mixed system. The interactions between CGS and Triton X‐100 were determined to be non‐ideal and synergistic. The calculated interaction parameters (βM) have negative values at all temperatures and for all mole fractions, showing attractive interactions. It was found that increasing the mole fraction of Triton X‐100 significantly increased the synergistic effect (more negative values). Micellar aggregation number (Nagg) values of pure surfactants and their mixtures in different ratios were obtained with the steady‐state fluorescence quenching method. Furthermore, the molar solubilization ratio of Sudan III organic dye in all surfactants aqueous systems was obtained using UV–Visible spectrophotometry. At concentrations above critical micelle concentration, the solubility of Sudan III in water was substantially increased linearly for all systems and it was observed that the enhancement was even more significant for mixed surfactant systems.

Calculation of screened Coulomb interaction parameters for the charge-disproportionated insulator CaFeO3

We calculate the screened electron-electron interaction for the charge-disproportionated insulator CaFeO3 using the constrained random-phase approximation (cRPA). While in many correlated materials the formation of a Mott-insulating state is driven by a large local Coulomb repulsion, represented by the Hubbard U, several cases have been identified more recently in which U is strongly screened and instead the Hund's interaction J dominates the physics. Our results confirm a strong screening of the local Coulomb repulsion U in CaFeO3, whereas J is much less screened and can thus stabilize a charge-disproportionated insulating state. This is consistent with the case of the rare-earth nickelates, where similar behavior has been demonstrated. In addition, we validate some common assumptions used for parametrizing the local electron-electron interaction in first-principles calculations based on density-functional theory (DFT), we assess the dependence of the interaction on the choice of correlated orbitals, and we discuss the use of the calculated interaction parameters in DFT+U calculations of CaFeO3. Our work also highlights certain limitations for the direct use of cRPA results in DFT-based first-principles calculations, in particular for systems with strong entanglement between the correlated and uncorrelated bands. Published by the American Physical Society 2024

Study on the properties of sodium lauroyl lactate anionic surfactant and cationic surfactant in a mixed system

The surface properties and applications of mixtures of an anionic surfactant (sodium lauroyl lactate (SLL)) and cationic surfactant (gemini quaternary ammonium salt with a hydroxyl group (GC12)) were investigated. The results showed that SLL/GC12 surfactant mixtures have synergistic effects, yielding higher surface activity and greater application performance. When the mole fraction of SLL (αSLL) was 0.4, the surface tension reached its minimum value. Furthermore, based on the calculated interaction parameters, stronger attractive interactions between the mixed SLL/GC12 surfactant molecules could be obtained at air/solution interfaces or with mixed micelles. When the mass fraction of SLL was 50%, its wetting ability and emulsifying capacity were optimal. The foam stability exceeded 95% when the mass fractions of SLL (WSLL) were 20%, 40%, and 50%. In addition, when the mole fraction of SLL was approximately 0.5, vesicles formed easily at a total solution concentration of 3 mM.

Self-Assembly, Interfacial, and Thermodynamic Properties of Antipsychotic Drug with Bile Salt in Water/Salt Solutions

Abstract Herein, we investigated the micelle formation of mixed systems of the antipsychotic drug, chlorpromazine hydrochloride (CPZ), and the bile salt, sodium deoxycholate (NaDC), both in the absence and presence of NaCl by tensiometry. To understand the aggregation behaviour of the mixture of these two amphiphiles, we calculated various micellar and interfacial parameters using the theories of Clint, Rubingh, Rosen and Motomura. The calculated interaction parameters indicate an attractive interaction between the two amphiphiles both in the absence and presence of salt. The results were discussed with regard to the use of bile salt as a promising drug carrier for CPZ and the improvement of its bioavailability.

Viscosity reduction of extra-heavy oil using toluene in water emulsions

Surfactants are widely used to reduce the viscosity of heavy oil by emulsification, but emulsification of an extra-heavy oil is difficult and does not even occur in some cases. A diluent is effective in reducing the viscosity of extra-heavy oil, but substantial volumes are required. In this work, we combined the advantages of a surfactant solution and a diluent in the form of emulsions to emulsify extra-heavy oil. The toluene/water (T/W) emulsion was prepared with mixed (AES-DOA) surfactants formed from an anionic surfactant (AES, alkyl polyoxyethylene ether sodium sulfate) and a gemini-like surfactant (DOA, prepared by mixing oleic acid and Jeffamine D 230). Compared with using toluene or AES-DOA surfactant solution alone to achieve the desired extra-heavy oil viscosity (30 ± 10 mPa·s), the T/W emulsion decreased toluene and surfactant dosage from 56 to 3 wt% and from 12 to 2 mmol/L, respectively. The effect of toluene and AES-DOA mixed surfactant on emulsification was analyzed by measuring the viscosity of the resultant extra-heavy oil emulsions. The results suggest that the addition of toluene reduced the viscosity of extra-heavy oil (dispersed phase) and accordingly contributed to emulsify extra-heavy oil. The synergistic effect of the AES-DOA mixed surfactants was evaluated by measuring the interfacial tension and calculating interaction parameters (βm) of the mixed surfactants formed at different AES mole fractions. When the mole fraction of AES was 0.6 in the mixture, the mixed surfactant possessed the highest interfacial activity and the largest negative βm, confirming the strongest synergistic effect. As a result, the best emulsification efficiency was achieved at this mole fraction. Increasing toluene content and AES-DOA mixed surfactant concentration was found to increase the emulsion stability against coalescence. The results from this study demonstrate that T/W emulsions prepared using the AES-DOA mixed surfactants can overcome the difficulties in emulsifying the highly viscous extra-heavy oil.

New group interaction parameters of the UNIFAC model for the solubility of water in fatty acid methyl esters and biodiesel

Water content is one of the most important quality indexes of biodiesel. In this study, the group interaction parameters of UNIFAC model are optimized to improve this model in predicting the solubility of water in fatty acid methyl esters and biodiesel. To determine the binary interaction parameters between water and the main functional groups attached to the molecules of the biodiesel compounds, 55 experimental data points related to the solubility of water in nine pure fatty acid methyl esters in the temperature range of 282.2 K–323.2 K are employed. Then, the model is used to predict the water solubility in 10 different biodiesels (60 data points), to evaluate the calculated interaction parameters in predicting the solubility of water in the mixture of fatty acid methyl esters. The average absolute relative deviations of the model in predicting the water content of pure fatty acid methyl esters and biodiesel are 4.31% and 4.69%, respectively. To show the superior performance of the model, the results of the model are compared with the results of previous models.

Solid state drug-polymer miscibility studies using the model drug ABT-102

Amorphous solid dispersions typically suffer storage stability issues due to: their amorphous nature, high drug loading, uneven drug:stabilizer ratio and plasticization effects as a result of hygroscopic excipients. An extensive solid state miscibility study was conducted to aid in understanding the mechanisms involved in drug/stabilizer interactions. ABT-102 (model drug) and nine different polymers with different molecular weights and viscosities were selected to investigate drug/polymer miscibility. Three different polymer:drug ratios (1:3, 1:1 and 3:1, w/w) were analyzed using: DSC, FTIR and PXRD. Three different techniques were used to prepare the amorphous solid dispersions: serial dilution, solvent evaporation and spray drying. Spray drying was the best method to obtain amorphous solid dispersions. However, under certain conditions amorphous formulations could be obtained using solvent evaporation. Melting point depression was used to calculate interaction parameters and free energy of mixing for the various drug polymer mixtures. The spray dried solid dispersions yielded a negative free energy of mixing which indicated strong drug-polymer miscibility compared to the solvent evaporation and serial dilution method. Soluplus was the best stabilizer compared to PVP and HPMC, which is probably a consequence of strong hydrogen bonding between the two CO moieties of soluplus and the drug NH moieities.

Investigations on zwitterionic alkylsulfobetaines and nonionic triton X-100 in mixed aqueous solutions: Effect on size, phase separation and mixed micellar characteristics

Zwitterionic sulfobetaine surfactants are widely applied in industries dealing with personal care products, mainly due to an advantage of minimal irritating effects to skin as compared to ionic surfactants. We investigate on the aqueous solution behaviour of zwitterionic surfactant, namely alkyl N,N-dimethyl-3-ammonio-1-propanesulfonate (CnPS, n=10, 12, 14, 16) in pure and mixed state with Triton X-100 (non-ionic surfactant) by using surface tensiometry, dynamic light scattering (DLS) and cloud point measurements. The critical micelle concentration (CMC) for aqueous CnPS solutions decreases with corresponding increase in alkyl chain length and is also accompanied by an increase in aggregation number. The calculated interfacial parameters for binary mixed aqueous systems involving zwitterionic surfactant and TX-100 depict almost independent behaviour of πCMC and Γmax, indicating a non-associative ideal mixing. The calculated interaction parameter (βm) for TX-100+CnPS mixed system reveals insignificant deviation from ideal behaviour as confirmed by calculated values in proximity to zero. As concluded from size measurements using DLS, the apparent hydrodynamic size of the mixed micelles decreases with gradual addition of alkylsulfobetaines due to demicellization of formerly present ellipsoidal aggregates of TX-100. The clouding temperature of formed mixed micelles increases on gradual addition of CnPS due to corresponding increase of ionic charge and accordingly improved solubility. It is assumed that electrically neutral nature of sulfobetaines confines its electrostatic interactions with non-ionic TX-100 and accordingly deters feasible interactions leading to synergism.

Determination of Solvent–Polymer and Polymer–Polymer Flory–Huggins Interaction Parameters for Poly(3-hexylthiophene) via Solvent Vapor Swelling

We report the use of solvent vapor swelling of ultrathin polymer films to determine Flory–Huggins solvent–polymer and polymer–polymer interaction parameters (χi–j) for poly(3-hexylthiophene) (P3HT) and polystyrene (PS) over a wide solvent composition range. From the calculated interaction parameters, we constructed a polymer/polymer/solvent phase diagram that was validated experimentally. χtetrahydrofuran–P3HT (1.04 ± 0.04) and χCHCl3–P3HT (0.99 ± 0.01) were determined through swelling of ultrathin P3HT films. Similar experiments using PS films gave χtetrahydrofuran–PS = 0.41 ± 0.02 and χCHCl3–PS = 0.39 ± 0.01, consistent with literature values. As expected, these χi–j parameters indicated that P3HT is less compatible than PS with either solvent. From δPS (17.9 ± 0.2 MPa1/2) and δP3HT (14.8 ± 0.2 MPa1/2), determined through regular solution theory, we calculated χPS–P3HT = 0.48 ± 0.06 at 23 °C. The resulting phase diagram was validated by solution-based transmission measurements of PS/P3HT blends in o-xyl...

Investigation and correlation of physical stability, dissolution behaviour and interaction parameter of amorphous solid dispersions of telmisartan: A drug development perspective

The aim of this study was to investigate if amorphous solid dispersions of telmisartan, prepared in presence of different polymers, exhibit different structural and thermodynamic characteristics and whether these differences can be correlated to their physical stability (time to crystallisation) and dissolution behaviour. Amorphous samples were prepared by melt quenching. The resulting amorphous materials were characterised using X-ray diffraction, Raman spectroscopy and differential scanning calorimetry. All freshly prepared samples were completely X-ray amorphous (with a halo being the only feature in the diffractograms). The shape of the halos in the diffractograms varied suggesting structural variations in the near order of the molecules between the different amorphous solid dispersions (ASDs). Principal component analysis of the Raman spectra of the various ASD revealed that the samples clustered in the scores plot, again suggesting structural differences due to the presence of different drug–polymer interaction. The ranking of the samples with respect to physical stability and interaction parameter was: ASD of telmisartan:eudragit>ASD of telmisartan:soluplus>ASD of telmisartan:HPMC>ASD of telmisartan:PVP>amorphous telmisartan. The interaction parameter, calculated by using the Flory Huggins theory, showed a good correlation with the experimentally determined stability whereas a weak correlation was found with dissolution behaviour of different ASD. This study showed that correlation of physical stability and dissolution behaviour with calculated interaction parameter is possible for the same amorphous systems prepared by using different polymers. This could aid in selecting the most appropriate polymer for the development of optimised formulations containing amorphous drugs. It can be concluded that ASD prepared by using different polymers have different structural and thermal properties. These differences affect the physical stability and dissolution profiles of the amorphous solids. Thus, choosing the right polymer for preparing ASD is critical for producing materials with desired dissolution profiles and enhanced stability.

Co-nonsolvency effect of thermosensitive N-isopropylacrylamide nanometer-sized gel particles in water–PEG systems

Nanometer-sized N-isopropylacrylamide (NIPA) gel particles were prepared by precipitation polymerization, and their thermosensitive swelling behaviors in water–poly(ethylene glycol) (PEG) (MW = 200, 400) systems were investigated using photon correlation spectroscopy (PCS). The volume transition temperature decreased with increasing PEG concentration, and a completely unexpected swelling behavior was observed at high PEG concentrations. The cloud points of poly(N-isopropylacrylamide) (PNIPA) in water–PEG systems were also determined by thermo-optical analysis (TOA) in order to compare the volume transition temperatures of gel particles with the phase transition temperatures of linear PNIPA in given solvent mixtures. A lattice-based molecular thermodynamic framework was employed to calculate interaction parameters from binary liquid–liquid equilibria (LLE), and those parameters were then applied directly to describe the co-nonsolvency effects of the ternary solutions. By combining the molecular thermodynamic model for the mixing contribution with the Flory–Rehner (FR) model for the elasticity contribution, the reentrant swelling equilibria at various temperatures were calculated. Using only one adjustable parameter, we were able to describe the swelling behaviors at high temperature regions (above the LCST). Lastly, the predicted results were compared to PEG (MW = 200, 1000) selectivity data inside NIPA gel, and were found to be in good agreement with the proposed model without further adjustable parameters.

αs-Casein–PE6400 mixtures: a fluorescence study

Micelles are a potential encapsulation system for bioactive compounds. In previous studies we were able to show that the triblock copolymer PEO13-PPO30-PE013 and alphas-casein are miscible within distinct temperature and concentration ranges. In this study, we wanted to test our hypothesis that mixed micelles are formed which, in turn, are able to solubilize hydrophobic compounds. Additionally we want to gain insight into the specific arrangement of individual molecules in these micelles. For that purpose, mixtures containing increasing mole fractions of casein (alphacas = 4.3 x 10(-4) to alphacas = 7.2 x 10(-3)) were examined at 30 degreeC. The hydrophobic fluorescence probe pyrene was used as a model solute. Emission spectra were recorded and I1/I3 and lex/I1 ratios were evaluated. Furthermore, the emission spectra of tryptophan were recorded and the maximum emission wavelength was evaluated. The determined parameters showed that micelles are formed in all solutions and that the solubilization of pyrene occurred. The calculated interaction parameter betaindicated that the mixing was antagonistic, possibly due to steric hindrances between the casein and the polymer. It seems that the mixed micelles are formed in such a way that the hydrophobic part of the polymer is attached to the hydrophobic parts of the caseins (a necklace and bead model) since the tryptophan residues are located in a hydrophobic environment above the CMC. We suggest a first structural arrangement model, recognizing that further studies will be required to prove and refine it.

Dissipative particle dynamics investigation of microencapsulated thermal energy storage phase change materials

Phase change material (PCM), has been widely researched in many previous works, shows a good potential for thermal energy storage. The present paper investigated the mesoscopic morphologies and evolution mechanism of microencapsulated phase change materials (MEPCMs) using dissipative particle dynamics (DPD) simulations, which has rarely been performed in PCM related studies. The adequate coarse-grained and Flory-Huggins-type models were used to replace the molecular structures and calculate interaction parameters. The MEPCMs were fabricated with methyl trimethoxysilane (MTMS), 3-aminopropyl trimethoxysilane (APTMS) and n-eicosane in watery environment. The results showed that the simulated final configuration presented a cylindrical structure when the relative amount of water is less than the desired value. The size of the encapsulation decreased with the increasing of water concentration and increased with the increasing of core material concentration. The rational proportion of the components can be optimized or confirmed by the DPD simulations. The research indicates that the DPD simulation is an effective method for understanding the encapsulation process.

Gas-solid phase calculations of binary mixtures using optimization of evolutionary algorithms

A comparison between different modern populations based optimization methods applied to the gas-solid phase calculations is presented. Simulations are carried out in twelve binary mixtures containing supercritical carbon dioxide. Particle swarm optimization (PSO) and genetic algorithm (GA) are used to calculate interaction parameters, solubility, and sublimation pressure on these mixtures using the Peng-Robinson equation of state with the Wong-Sandler mixing rules. Comparing PSO with GA shows that the performance of PSO is better than that of GA and that it is a preferable method to optimize parameters of the gas-solid equilibrium.

Thermodynamic interactions of three SBS (styrene–butadiene–styrene) triblock copolymers with different solvents, by means of intrinsic viscosity measurements

The Hansen Solubility Parameter (HSP) and the Flory Huggins polymer–solvent interaction parameter of three SBS (styrene–butadiene–styrene triblock copolymer) rubbers have been determined by using intrinsic viscosity (IV) measurements. The obtained values indicated that, although all the tested compounds could be adequate as solvents, the aromatic ones are the most compatible for this kind of polymers. From these previous data, the activity coefficients of the solvent were also obtained and fitted to NRTL model. The calculated interaction parameters have a great importance in order to model, for example, the separation steps in the process of obtaining the rubber.

Gas adsorption on quasicrystalline surfaces

The low-friction properties of quasicrystal surfaces suggest their use as coatingson moving machine parts, including those in internal combustion engines. Insuch applications, additional lubricants are typically used. Since the low-frictionproperties of quasicrystals are thought to depend on their aperiodic structures, theinteractions of lubricants on quasicrystalline surfaces may have an impact on theirfrictional properties. In this paper, we address the fundamental issues that affect thegrowth and structural properties of gases on a quasicrystal surface. Studies of theadsorption and growth of rare gases on quasicrystal surfaces are reviewed, andnew results are presented for the modeling and simulation of hydrocarbons onquasicrystal surfaces. The calculated interaction parameters are presented for methaneadsorption on ten-fold Al–Ni–Co. Methane is found to form aperiodically orderedstructures, consistent with the rules established earlier for rare gases on Al–Ni–Co.

Binary mixtures of (β-C12G2) with cationic and non-ionic surfactants: micelle and surface compositions.

Surfactants used for practical applications are usually surfactant mixtures because they often exhibit a performance that is superior to the individual surfactants. In the present study binary mixtures of the sugar based surfactant n-dodecyl-β-D-maltoside (β-C12G2) with the cationic surfactant dodecyl trimethylammonium bromide (C12TAB) and the non-ionic hexaethylene-glycol dodecyl ether (C12E6), respectively, were investigated at different bulk mole fractions. Surface tension measurements were used to determine the critical micelle concentration and the surfactant composition at the surface. In addition, the regular solution theory was used to calculate interaction parameters as well as the mole fractions of the individual surfactants in the mixed air-water monolayer and in the mixed micelles, respectively. It was found that n-dodecyl-β-D-maltoside interacts weakly with the cationic surfactant (C12TAB) and that it dominates in both the mixed monolayer and the mixed micelles. On the other hand, β-C12G2 and C12E6 mix ideally in solution. For both surfactant mixtures the surfactant composition at the surface determined by surface tension measurements and by the regular solution theory, respectively, were compared and discussed in detail.

Interfacial and Thermodynamic Properties of Anionic‐Nonionic Mixed Surfactant System: Influence of Hydrophobic Chain Length of the Nonionic Surfactant

The influence of hydrophobic chain length in nonionic surfactants on interfacial and thermodynamics properties of a binary anionic‐nonionic mixed surfactant was investigated. In this study, nonionic surfactants lauric‐monoethanolamide (C12 MEA) and myrisitic‐monoethanolamide (C14 MEA) were mixed with an anionic surfactant, α‐olefin sulfonate (AOS). The critical micelle concentration (cmc), maximum surface excess (Γmax), and minimum area per molecule (Amin) were obtained from surface tension isotherms at various temperatures. The thermodynamic parameters of micellization and adsorption were also computed. Micellar aggregation number (Nagg), micropolarity, and binding constant (Ksv) of pure and mixed surfactant system was calculated by fluorescence measurements. Rubingh's method was applied to calculate interaction parameters for the mixed surfactant systems.