Solubility of pharmaceuticals: A comparison between SciPharma, a PC-SAFT-based approach, and NRTL-SAC

The solubility of seven pharmaceutical compounds (paracetamol, benzoic acid, 4-aminobenzoic acid, salicylic acid, ibuprofen, naproxen and temazepam) in pure and mixed solvents as a function of temperature is calculated with SciPharma, a semi-empirical approach based on PC-SAFT, and the NRTL-SAC model. To conduct a fair comparison between the approaches, the parameters of the compounds were regressed against the same solubility data, chosen to account for hydrophilic, polar and hydrophobic interactions. Only these solubility data were used by both models for predicting solubility in other pure and mixed solvents for which experimental data were available for comparison. A total of 386 pure solvent data points were used for the comparison comprising one or more temperatures per solvent. SciPharma is found to be more accurate than NRTL-SAC on the pure solvent data used especially in the description of the temperature dependence. This is due to the appropriate parameterization of the pharmaceuticals and the temperature-dependent description of the activity coefficient in PC-SAFT. The solubility in mixed solvents is predicted satisfactorily with SciPharma. NRTL-SAC tends to overestimate the solubility in aqueous solutions of alcohols or shows invariable solubility with composition in other cases

Experimental and molecular dynamics simulation study on thermal, transport, and rheological properties of asphalt

© 2020 Elsevier Ltd The purpose of this study was to evaluate the thermal (glass transition temperature), transport (self-diffusion), and rheological (viscosity, storage and loss modulus) properties of asphalt via laboratory experiments and molecular dynamics simulations. A 12-component asphalt model was employed in the molecular dynamics simulations with the modified Amber-Cornell force field. The asphalt model with the specific force field was validated against experimental and literature density data at various temperatures. The transition from the glassy state to the viscoelastic regime was explored by calculating the glass transition temperature. The results were compared with results from the differential scanning calorimeter (DSC) experiments. The self-diffusivity was calculated at a broad temperature range. The viscosity at the viscoelastic liquid regime was measured in the laboratory and calculated with reverse non-equilibrium molecular dynamic (rNEMD) simulations at various temperatures. Laboratory dynamic shear rheological testing was conducted for a wide frequency range at 70 °C. Oscillatory shear was applied in the asphalt model for calculating the storage and loss moduli within the experimental frequency range

Understanding of Structural and Surface Tension Properties of Asphalt Model Using Molecular Dynamics Simulation

The objective of this study is to characterize the molecular structural and surface tension properties of asphalt model using molecular dynamics (MD) simulation. The previously proposed 12-component asphalt model (AAA-1) was used in the MD simulation to evaluate the surface tension and structural properties in the molecular level of asphalt at different temperatures. The calculated densities from the asphalt models were in good agreement with the reference data. The asphalt model was validated with this comparison. The surface tension was predicted from the MD models and compared with the with the pendant drop test methods. The results showed the reasonable comparison. The molecular structural properties of asphalt model mainly on the radial distribution function (RDF) was also investigated. The first peaks and the highest peaks between groups of molecules identified the most contributed atom pairs in the asphalt group models which have general agreement with references. Based on these, the proposed MD simulations provide insights to understand the molecular structural and surface tension properties of asphalt at different temperatures

Experimental and molecular modeling evaluation of the physicochemical properties of proline-based deep eutectic solvents

The liquid range and applicability of deep eutectic solvents (DESs) are determined by their physicochemical properties. In this work, the physicochemical properties of glycolic acid:proline and malic acid:proline were evaluated experimentally and with MD simulations at five different ratios. Both DESs exhibited esterification upon preparation, which affected the viscosity in particular. In order to minimize oligomer formation and water release, three different experimental preparation methods were explored, but none could prevent esterification. The experimental and calculated densities of the DESs were found to be in good agreement. The measured and modeled glass transition temperature showed similar trends with composition, as did the experimental viscosity and the calculated diffusivities. The MD simulations provided additional insight at the atomistic level, showing that at acid-rich compositions, the acid-acid hydrogen bonding (HB) interactions prevail. Malic acid-based DESs show stronger acid-acid HB interactions than glycolic acid-based ones, possibly explaining its extreme viscosity. Upon the addition of proline, the interspecies interactions become predominant, confirming the formation of the widely assumed HB network between the DESs constituents in the liquid phase

Experimental and molecular modeling evaluation of the physicochemical properties of proline-based deep eutectic solvents

\u3cp\u3eThe liquid range and applicability of deep eutectic solvents (DESs) are determined by their physicochemical properties. In this work, the physicochemical properties of glycolic acid:proline and malic acid:proline were evaluated experimentally and with MD simulations at five different ratios. Both DESs exhibited esterification upon preparation, which affected the viscosity in particular. In order to minimize oligomer formation and water release, three different experimental preparation methods were explored, but none could prevent esterification. The experimental and calculated densities of the DESs were found to be in good agreement. The measured and modeled glass transition temperature showed similar trends with composition, as did the experimental viscosity and the calculated diffusivities. The MD simulations provided additional insight at the atomistic level, showing that at acid-rich compositions, the acid-acid hydrogen bonding (HB) interactions prevail. Malic acid-based DESs show stronger acid-acid HB interactions than glycolic acid-based ones, possibly explaining its extreme viscosity. Upon the addition of proline, the interspecies interactions become predominant, confirming the formation of the widely assumed HB network between the DESs constituents in the liquid phase.\u3c/p\u3

Tailoring waterborne coating rheology with hydrophobically modified ethoxylated urethanes (HEURs) : molecular architecture insights supported by CG-MD simulations

A novel investigation of the effects of the hydrophilic and hydrophobic segments of hydrophobically modified ethoxylated urethanes (HEURs) on the rheological properties of their aqueous solutions, latex-based emulsions, and waterborne paints is demonstrated. Different HEUR thickeners were produced by varying the poly(ethylene glycol) (PEG) molecular weight and terminal hydrophobic size. Results reveal that the strength of hydrophobic associations and, consequently, the rheological properties of HEUR formulations can be effectively controlled by modifying the structure of the hydrophobic segment, specifically, the combination of diisocyanate and monoalcohol. This allows for the on-demand attainment of diverse rheological behaviors ranging from predominantly Newtonian profiles exhibiting lower viscosities to markedly pseudoplastic behaviors with significantly higher viscosities. The length of the hydrophilic group appears to affect viscosity only marginally up to a molecular weight of 23,000 g/mol, with more notable effects at 33,000 g/mol. Additionally, it was indicated that the rheological responses observed in water solutions provide a reliable forecast of their behavior in latex-based emulsions and waterborne paints. Coarse-grained molecular dynamics (CG-MD) simulations were also applied to gain insight into HEUR micelle dynamics in aqueous solutions. Guided by the DBSCAN algorithm, the simulations successfully captured the concentration-dependent behavior and the impact of hydrophilic chain length, aligning with the experimental viscosity trends. Various metrics were employed to provide a comprehensive analysis of the micellization process, including the hydrophobic cluster volume, the total micellar volume, the aggregation number, and the number of chains interconnecting with other micelles

Experimental and Molecular Modeling Evaluation of the Physicochemical Properties of Proline-Based Deep Eutectic Solvents

The liquid range and applicability of deep eutectic solvents (DESs) are determined by their physicochemical properties. In this work, the physicochemical properties of glycolic acid:proline and malic acid:proline were evaluated experimentally and with MD simulations at five different ratios. Both DESs exhibited esterification upon preparation, which affected the viscosity in particular. In order to minimize oligomer formation and water release, three different experimental preparation methods were explored, but none could prevent esterification. The experimental and calculated densities of the DESs were found to be in good agreement. The measured and modeled glass transition temperature showed similar trends with composition, as did the experimental viscosity and the calculated diffusivities. The MD simulations provided additional insight at the atomistic level, showing that at acid-rich compositions, the acid–acid hydrogen bonding (HB) interactions prevail. Malic acid–based DESs show stronger acid–acid HB interactions than glycolic acid–based ones, possibly explaining its extreme viscosity. Upon the addition of proline, the interspecies interactions become predominant, confirming the formation of the widely assumed HB network between the DESs constituents in the liquid phase

Effect of Oxygenation on Carbon Dioxide Absorption and Thermophysical Properties of Ionic Liquids: Experiments and Modeling Using Electrolyte PC-SAFT

The thermophysical properties (decomposition temperature, glass transition temperature, density, and viscosity) of imidazolium-based ionic liquids (ILs) paired with the tricyanomethanide ([TCM]⁻) anion and the bis­(trifluoromethylsulfonyl)­imide ([Tf₂N]⁻) anion were studied within a wide temperature range. The effect of the ether functional group (in [Tf₂N]⁻ and [TCM]⁻ ILs) and hydroxyl functional group (in [Tf₂N]⁻ IL) incorporated in the cation’s alkyl chain on the thermophysical behavior and carbon dioxide (CO₂) solubility was evaluated by comparing their behavior to the corresponding nonfunctionalized ILs. The thermal stability was enhanced by the inclusion of hydroxyl functionalization in the cation’s alkyl chain while ether functionalization had no major effect on the thermal stability. The ether groups (one or two) resulted in an increase in the density and a decrease in the viscosity of all ILs. The hydroxyl group resulted in an increase in both properties. The CO₂ solubilities were not affected by the presence of the ether groups, while the hydroxyl group led to a significant decrease in the solubility. Additionally, the electrolyte perturbed-chain statistical associated fluid theory (ePC-SAFT) equation of state was used to calculate the CO₂ solubility in the ILs and the Henry’s law constant. The model showed great predictive ability. The Henry’s constants were applied to calculate the partial molar thermodynamic properties of solvation