Infinite Dilution Research Articles

Investigation of thermodynamic and solubility properties of poly (4-methyl styrene - alt - maleic anhydride) and poly (4-methyl styrene - alt - n-propyl maleimide) copolymers by inverse gas chromatography.

Poly (4-methyl styrene - alt - maleic anhydride) (PMS-A) copolymer was synthesized by free radical polymerization, and then modified with n-propyl amine through ring opening of maleic anhydride units to prepare modified poly (4-methyl styrene - alt - n-propyl maleimide) (PMS-I) copolymer. FT-IR analysis confirmed the composition of these copolymers. Thermogravimetric analysis (TGA), glass transition temperature (Tg), and gel permeation chromatography (GPC) were investigated for the copolymers. Some thermodynamic and physicochemical properties were determined for different groups of test solutes at infinite dilution by inverse gas chromatography (IGC) in the temperature ranges 373-393 K and 373-433 K for the PMS-A and the PMS-I copolymers, respectively. The physicochemical characterization of the IGC included the determination of the molar heat enthalpy of sorption, mixing and vaporization (ΔH1S,ΔH1∞,ΔHV), weight fraction activity coefficient,Ω1∞, Flory-Huggins interaction parameters, X12∞ at infinite dilution, Hildebrand solubility parameter, δ2, total and partial Hansen solubility parameters, δT,δd,δp,δh. The results showed that the solubility of the PMS-A copolymer in nonpolar solutes is poor but moderate for the PMS-I copolymer. The solubility of the PMS-A copolymer in benzene and toluene solutes is moderate, but it is good for the PMS-I copolymer. The solubility of the PMS-A copolymer in ketones, halogens, nitriles, acetates, heterocyclic, and alcohol solutes is good, but the solubility of the PMS-I copolymer with these solutes is the best. Values of the Hildebrand solubility parameters of the PMS-A and PMS-I copolymers ranged from 17.57 - 16.73 and 19.48 - 18.06, respectively. In addition, the total Hansen solubility parameters ranged from 18.82 - 17.12 and 16.65 - 15.20.

Scalable and accurate simulation of electrolyte solutions with quantum chemical accuracy.

Abstract Electrolyte solutions play critical role in a vast range of important applications, yet an accurate and scalable method of predicting their properties without fitting to experiment has remained out of reach, despite over a century of effort. Here, we combine state-of-the-art density functional theory and equivariant neural network potentials to demonstrate this capability, reproducing key structural, thermodynamic, and kinetic properties. We show that neural network potentials (NNPs) can be recursively trained on a subset of their own output to enable coarse-grained/continuum-solvent molecular simulations that can access much longer timescales than possible with all atom simulations. We observe the surprising formation of Li cation dimers along with identical anion-anion pairing of chloride and bromide anions. Finally, we simulate the crystal phase and infinite dilution pairing free energies despite being trained only on moderate concentration solutions. This approach should be scaled to build a greatly expanded database of electrolyte solution properties than currently exists.

Dynamic Light Scattering Analysis of Lipid Nanoparticles: Effect of Salts on the Diffusion Interaction Parameter and Hydrodynamic Radius at Infinite Dilution.

The rise in the popularity of lipid nanoparticle (LNP)-based formulations necessitates the need for screening tools to quickly predict their colloidal stability in the presence of common excipients. Protein chemists have employed the diffusion interaction parameter (kD) determined using dynamic light scattering as an indicator of formulation stability, yet this approach has not been applied to particulate systems. Herein, kD measurements of LNPs revealed behavior dissimilar to that of proteins. LNP interactions were inherently weakly attractive and unaffected by increasing concentrations of NaCl. The small change in the value in the presence of different salts was dependent upon salt molecular identity and consistent with the Hofmeister series. In addition, calculation of the hydrodynamic radius at infinite dilution (RH,0) revealed a slight reduction in the LNP size with increasing NaCl concentration. Overall, while traditional kD measurements provide limited information about LNP stability, the assay provides insight into physical changes to LNP in the presence of excipients via extrapolation of the diffusion coefficient to infinite dilution.

Solvation Structure and Dynamics of the Thiocyanate Anion in mixed N,N-Dimethylformamide-Water Solvents: A Molecular Dynamics Approach.

The solvation structure and dynamics of the thiocyanate anion at infinite dilution in mixed N, N-Dimethylformamide (DMF)-water liquid solvents was studied using classical molecular dynamics simulation techniques. The results obtained have indicated a preferential solvation of the thiocyanate anions by the water molecules, due to strong hydrogen bonding interactions between the anion and water molecules. A first hydration shell at short intermolecular distances is formed around the SCN- anion consisting mainly by water molecules, followed by a second shell consisting by both DMF and water molecules. The strong interactions between the thiocyanate anion and water molecules are further reflected upon the calculated intermittent residence lifetimes of water and DMF in the first and second solvation shells. The dependence of the reorientational relaxation times of the thiocyanate anion upon the mole fraction of DMF in the mixtures has been found to be in good agreement with experiment, revealing strong concentration effects upon these relaxation phenomena. An appreciable solvent composition effect upon the low frequency intermolecular vibrations, due to the anion-water interactions, has also been revealed by calculating the atomic velocity correlation functions and corresponding spectral densities of the anion.

On the Solvation Properties of Menthol-Thymol Mixtures. A Molecular Dynamics Investigation.

Using classical molecular dynamics, we have investigated the solvation of catechol, resorcinol, hydroquinone and 1,4-benzoquinone at infinite dilution, in a series of menthol - thymol mixtures in which the molar fraction of thymol (xTHY) has been increased by steps of 0.1, from 0 (pure menthol) to 1 (pure thymol). The evolution of the solvation shell around the solutes reveals that when xTHY is increased, the average number of hydrogen bonds (HB) where the solute acts as HB acceptor (HBA) and the solvent as HB donor (HBD) increases, while the amount of HB, in which the solute acts as HBD and the solvent as HBA, decreases. Overall, the total number of HBs between the different benzenediols and the solvent decreases with an increase of xTHY, while for benzoquinone the total number of HB increases. This points to the fact that "acidic" or HBD molecules are better solvated in mixtures with high menthol proportion, while "basic" or HBA molecules, are better solvated in thymol rich mixtures. The results reported herein follow the same trends as experimentally reported Kamlet-Taft parameters and present insights on how the composition of these "deep eutectic" mixtures maybe tweaked in order to optimize their solvation properties.

Relating the Salt Thermodynamic Factor to Solvent Activities in Ternary Multi-Solvent Electrolytes

The activities of individual solvent species in multi-solvent ternary liquid electrolytes dictate liquid-solid equilibria and are pertinent to transport phenomena. Nonetheless, considerable scholarship has assumed that such electrolytes can be modeled as single-solvent electrolytes. Relaxing this assumption, we show in the present work that knowledge of the activity of ionic species, described by the salt thermodynamic factor and the transfer activity coefficients at infinite dilution, is sufficient to calculate activity changes of individual solvent species for ternary multi-solvent electrolytes. We also propose measurements of an individual solvent species activity as a method to study (ionic) solvent transfer energies. We apply the derived relationships to the well-characterized liquid electrolyte system LiCl in H2O-EtOH. We also study a non-aqueous electrolyte solution, LiPF6 in EC-EMC, which is important for lithium-ion battery technology. For the latter, we show that in the studied composition space there are non-negligible transfer activity coefficients, highlighting the importance of a multisolvent description of the ternary electrolytes.

Dissipative particle dynamics parametrisation using infinite dilution activity coefficients: the impact of bonding.

Dissipative particle dynamics (DPD) simulations have proven to be a valuable coarse-grained simulation technique for studying complex systems such as surfactant and polymer solutions. However, the best method to use in parametrising DPD systems is not universally agreed. One common approach is to map infinite dilution activity coefficients to the DPD simulation 'beads' that represent molecular fragments. However, we show that here that this approach can lead to serious errors when bonding beads together to create molecules. We show errors arise from the verlaps between bonded beads, which alters their solubility. In this article, we demonstrate how these bonding errors can be accounted for when defining DPD force fields using simple theoretical methods to account for the overlapping volumes, and we demonstrate the validity of our approach by calculating the partition coefficients for a series of solutes into two immiscible solvents.

Application of a New Thermal Model for the Determination of London Dispersive Properties of H-β-Zeolite/Rhodium Catalysts Using New 2D Chromatographic Models.

A new methodology based on the Hamieh thermal model was applied for the determination of the surface properties of solid surfaces. The new approach consisted of the accurate quantification of the London dispersive surface energy of materials using the two-dimensional inverse gas chromatography technique at infinite dilution. This technique used the notion of the net retention volume of adsorbed molecules on the solid catalysts, allowing the determination of the free energy of adsorption. The Hamieh thermal model proving the temperature effect on the surface area of organic molecules adsorbed on H-β-zeolite/rhodium catalysts at different rhodium percentages was used to determine the accurate values of the London dispersive surface energy of solid surfaces at different temperatures. This new method also allowed a precise evaluation of the dispersive adhesion work, dispersive surface enthalpy, and entropy of adsorption of n-alkanes adsorbed on the catalysts. In this paper, the London dispersive surface energy and adhesion work of H-β-zeolite-supported rhodium catalysts were determined using the free energy of adsorbed molecules obtained from the two-dimensional inverse gas chromatography technique at infinite dilution. It was proved that the London dispersive surface energy strongly depended on the temperature and the rhodium percentage, while the dispersive adhesion work of n-alkanes adsorbed on H-β-zeolite/rhodium catalysts was proved to be a function of the temperature, rhodium percentage, and the carbon atom number of the n-alkanes.

Robust Method for Property Prediction via Artificial Neural Networks: Incorporating Key Structural Features for Carbon Dioxide-Ionic Liquid Mixtures.

This study addresses a critical gap in the existing literature on carbon dioxide and ionic liquid (IL) mixtures, where fragmented and incomplete data, particularly for flow properties, hinder practical applications. Therefore, this work aimed to establish a robust and efficient method for predicting the density of the CO2-IL mixtures across diverse operating conditions and IL families using novel validation techniques. Both linear and symbolic regression models provided relevant insights but failed to accurately capture the IL-CO2 interactions in a mixture that determine the molar volume of CO2 at infinite dilution when solubilized by a given IL. Therefore, more mathematically flexible artificial neural networks (ANN) were trained based on three different sets of features: (1) IL critical properties, (2) IL structural descriptors, and (3) a selective combination of (1) and (2). While all models showed relative deviations consistently below 3% for the testing data, combining critical and structural data significantly improved accuracy (R2 = 0.986, testing data set). A postprocessing outlier-handling method enhanced model performance, removing a minimal fraction (below 0.2%) of unphysical data points. Furthermore, molecular dynamics simulations validated the robust generalization of all ANN models, with the combined model exhibiting remarkable accuracy over operating conditions outside the training ranges for ILs in the training set and even for ILs that are not included in this data set. This computational approach provides a significantly faster and broader alternative to other thermodynamical tools, establishing a solid method for future machine learning (ML)-based property prediction augmented by external validation from cross-comparison tests and statistical thermodynamics models.

Vulcanization Accelerators and Silica Coupling Agents in Polyisoprene Melts.

The achievement of sufficient dispersion of vulcanization accelerators is critical to tailoring superior cross-linked elastomers. Modern recipes rely on multicomponent formulations with silica particles covered by coupling agents. We study the molecular properties of select accelerators in polyisoprene melts and their affinity for functionalized surfaces via extensive all-atom molecular dynamics simulations. We focus on the common (N-cyclohexyl)-2-benzothiazole sulfenamide (CBS), 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane (DBTH), and diphenyl guanidine (DPG) molecules and their mixing characteristics at curing temperatures. Our results support a low self-association affinity for CBS and DBTH within polyisoprene, whereas DPG forms small hydrogen-bonded aggregates. Subsequently, we examine systems in contact with silica interfaces, bare or grafted with (3-mercaptopropyl)triethoxysilane (MPTES), (3-octanoylthio) 1-propyl-triethoxysilane (NXT), and bis[3-(triethoxysilyl)propyl]disulfide (TESPD). Accelerator-substrate affinity is first assessed at infinite dilution using free energy calculations and subsequently at finite concentrations. Accelerators exhibit high substrate affinity (DPG > CBS > DBTH) irrespective of functionalization. However, coupling agents are able to displace from the surface a significant amount that increases with the grafting density and the size of the coupling agent. Finally, we investigate the behavior of DPG in binary DPG-CBS formulations, where the former can act as a covering agent that solubilizes CBS into the bulk polymer.

Activity Coefficients and Partial-Molar Heats of Mixing at Unlimited Dilution of the Components for the Dimethylzinc - Dimethyl Telluride System

Using a semi-empirical model, the vapor-liquid equilibrium is described in the dimethylzinc-dimethyl telluride system: the activity coefficients of the solution components and the partial-molar heats of mixing at infinite dilution are calculated. The primary data for the application of the semi-empirical model were obtained by us from measuring the temperature dependence of the saturated vapor pressure of highly pure samples of dimethylzinc, dimethyl telluride and their solutions.

Extractive rectification using DES for benzene‐cyclohexane‐cyclohexene ternary azeotropic system

AbstractBACKGROUNDBenzene, cyclohexane, and cyclohexene are ternary azeotropic systems, which cannot achieve high‐purity separation by ordinary distillation, but this issue can be solved by extractive distillation. Deep Eutectic Solvents (DES) is a ‘green solvent’ that has emerged in recent years and is often used as an extractant.RESULTSIn this study, the COSMO‐SAC solvation model was used to calculate the infinite dilution activity coefficients (γ∞) of DES with different compositions to screen suitable DES, and the effect was demonstrated by vapor–liquid equilibrium experiment (VLE). In addition, the effect of intermolecular interactions was explored in this study by means of independent gradient (IGM) equivalence plot, and process simulations were carried out by means of Aspen Plus software.CONCLUSIONVLE experiments showed that the combination of DES extractants tetrabutylphosphonium bromide: levulinic acid (1:4) and tetrabutylammonium bromide: cyclobutyl sulfone (1:4) could break the azeotropic relationship of benzene, cyclohexane, and cyclohexene ternary systems. In addition, using Aspen process simulation to compare the screened DES extractant with the industrially used dimethylacetamide (DMAC) extractant, the use of the screened DES extractant was able to reduce the condenser and reboiler energy consumption by 14.93%. © 2024 Society of Chemical Industry (SCI).

Thermodynamic evaluation of intermolecular interaction selectivity in separation of binary mixtures based on the activity coefficients at infinite dilution

Thermodynamic evaluation of intermolecular interaction selectivity in separation of binary mixtures based on the activity coefficients at infinite dilution

Exploring different interactions of biologically potent molecules L-aspartic acid and L-glutamic acid prevailing in aqueous antibiotic compound doxycycline hyclate by experimental and theoretical studies at various temperatures

Exploring different interactions of biologically potent molecules L-aspartic acid and L-glutamic acid prevailing in aqueous antibiotic compound doxycycline hyclate by experimental and theoretical studies at various temperatures

Investigation and characterization of deep eutectic solvent (DES) based stationary phase in gas chromatography

In this study, the preparation of the stationary phase based on the deep eutectic solvent (DES) was investigated along with the measurement of thermodynamic parameters. The physical characterization of the synthesized sample was investigated by Thermogravimetric (TGA), scanning electron microscope (SEM) and Fourier Transform Infrared Spectrometer (FTIR) analyses. Thermodynamic parameters measured to express the potential ability of the constructed stationary phase were McReynolds constants, partition coefficient, Abraham system constants, ∆, activity coefficient at infinite dilution (γi∞), and selectivity (Sij∞). For this purpose, the parameters were investigated in different amounts of stationary phase (SP) loading including 5, 10, 15 and 18 %w/w and also at three temperatures of 40, 70 and 100 °C. The prepared stationary phase with moderate polarity had the potential to separate BTEXs, aromatic compounds and alcohols due to strong interactions caused by hydrogen bonds. It was investigated the improved performance of the stationary phase prepared with carbowax. Finally, the performance of SP-DES stationary phase separation was investigated for different analytes including alkanes, alcohols and aromatic compounds.

Solvation phenomena in ternary system tetramethylurea-methylacetamide-water: Insights from volumetric, compressibility and FTIR analysis

Solvation phenomena in ternary system tetramethylurea-methylacetamide-water: Insights from volumetric, compressibility and FTIR analysis

Diffusion of organic solvents in thermoplastic elastomers: infinite dilution experiments

Diffusion of organic solvents in thermoplastic elastomers: infinite dilution experiments

Screening deep eutectic solvents as green solvents for efficient extraction of carbazole from model crude anthracene oil

Screening deep eutectic solvents as green solvents for efficient extraction of carbazole from model crude anthracene oil

New thermodynamic insights into pregabalin interactions with H+, Na+, Mg2+, Ca2+, Cu2+, Zn2+: Equilibrium constants, enthalpy changes and sequestering ability

New thermodynamic insights into pregabalin interactions with H+, Na+, Mg2+, Ca2+, Cu2+, Zn2+: Equilibrium constants, enthalpy changes and sequestering ability

Thermodynamic study of pyridoxine in different solvents and temperatures: DFT study

The equivalent conductivities (Λ) of B6 vitamin (pyridoxine) in HշՕ and MeOH were measured at different temperatures between 293 to 313 K, as well as in mixtures of H₂O and MeOH at percentages of 10, 20, 30, 40, and, 50% MeOH at 310 K. All the practical results were mathematically processed using the Lee Wheaton equation, which is applied to the derived conductivity of electrolytes with a similar composition (1:1). This equation calculates various conductivity components, including the equivalent conductance at infinite dilution (Λₒ), the ionic conductivity, the distance between ions (R), and also the constant of ionic aggregation (Ka) at best-fit values of (ϬΛ). The values of these parameters differed from one solvent to another depending on the molecular interactions in the solution and the physical properties of the solvents, such as viscosity and dielectric constant. Finally, thermodynamic quantities for the ion association reaction (ΔG°, ΔH°, and ΔS°) were also studied. Density functional theory (DFT) calculations (B3LYP/6-31G (d,p)) were employed to analyze vitamin B6 in the gas phase and diverse solvents. Three different continuum methods, namely AM1, PM3, and HF, were utilized, followed by DFT. The final method was utilized to explore the effects on its characteristics. KEY WORDS: Electrical conductivity, Lee-Wheaton equation, Theoretical chemistry, DFT. Bull. Chem. Soc. Ethiop. 2025, 39(1), 165-176. DOI: https://dx.doi.org/10.4314/bcse.v39i1.14