Solvent Interactions Research Articles

Computational Study on the Octahedral Surfaces of Magnetite Nanoparticles and Their Solvent Interaction.

Magnetite nanoparticles (MNPs) play an important role in geological and environmental systems because of their redox reactivity and ability to sequester a wide range of metals and metalloids. X-ray absorption spectroscopy conducted at metal and metalloid edges has suggested that the magnetite {111} faces of octahedrally shaped nanoparticles play a dominant role in the redox and sorption processes of these elements. However, studies directly probing the magnetite surfaces, especially in their fully solvated state, are scarce. Therefore, we investigated the speciation and stability over a wide Eh/pH range of octahedrally shaped MNPs of 2 nm size by means of Kohn-Sham density functional theory with Hubbard correction (DFT+U). By altering the protonation state of the crystals, a redox-sensitive response of the octahedrally coordinated Fe could be achieved. Furthermore, the preferential H distribution could be identified, highlighting the difference between the edges, vertices, and facets of the nanocrystals. Subsequently, the interactions of the MNPs with a solvent of pure water or a 0.5 M NaCl solution were studied by classical molecular dynamics (MD) simulations. Finally, a comparison of the corresponding macroscopic magnetite (111) surface to the investigated MNPs was conducted.

Chemical Resistance of Hydrogenated Nitrile Butadiene Rubber and Nitrile Butadiene Rubber in Propylene

Abstract The chemical resistance of hydrogenated nitrile butadiene rubber (HNBR) and nitrile butadiene rubber (NBR) in propylene is considered as no resistance (NR) by many chemical compatibility handbooks and industry chemical resistance tables and charts. This situation drives the change of the elastomer compounds from cheap HNBR/NBR to expensive fluoroelastomer (FKM) for applications involving propylene. However, in the literature, NBR and HNBR are rated as having good or excellent chemical resistance to all other hydrocarbons, such as ethylene, ethane, propane, butane, butylene. It seems that there are some special or unknown characters of propylene that make it is very harsh to both NBR and HNBR, and therefore it is important to investigate the chemical resistance of NBR and HNBR in propylene. In this study, the chemical resistance of HNBR and NBR in propylene is investigated according to ISO 23936-2 and ASTM D471. The test results are crucially important for the applications of HNBR/NBR in contact with propylene. Based on the tests, we investigated the changes of physical properties such as tensile properties, volume changes and glass transition temperatures and chemical structure of HNBR/NBR after aging in high-pressure propylene at an elevated temperature. The Hansen solubility parameters (HSP) of HNBR and NBR and many hydrocarbons such as ethylene, ethane, propylene, propane, butane, and butylene were estimated. Based on the HSP, the polymer solvent interaction parameters between HNBR/NBR and hydrocarbons were also estimated to explain the chemical resistance of HNBR/NBR in propylene. An aging mechanism was also proposed to explain the changes of HNBR and NBR in propylene aging. This study provided an even better guidance on chemical resistance of HNBR/NBR in propylene to the elastomer industry.

Rational Design of Two-Dimensional MA2Z4 Monolayers as Effective Anchoring Materials for Lithium-Sulfur Batteries.

Advances in lithium-sulfur batteries (LSBs) are impeded by the inefficiency of anchoring materials in facilitating long-term cycling and rate performance. To address this challenge, an exploration of two-dimensional MA2Z4 monolayers as potential anchoring materials for LSBs is proposed based on density functional theory calculations and machine learning (ML) techniques. Adsorption features, sulfur reduction reaction behaviors, and solvent interactions are assessed and analyzed; and MoGe2N4 and WGe2N4 are identified as the most promising candidates because they have optimal adsorption energies for lithium polysulfides to suppress the shuttle effect and exhibit enhanced catalytic activity. Meanwhile, ML analysis highlights the critical influence of the electronegativity of element Z in MA2Z4 on anchoring properties, providing valuable insights into future anchoring material design for high-performance LSBs.

PHYSICOCHEMICAL AND SPECTROSCOPIC ANALYSIS OF INTERACTIONS BETWEEN ASPIRIN AND NORMAL SALINE AT DIFFERENT TEMPERATURES

The primary goal of the current investigation is to explore the molecular interactions between the aspirin (2-Acetoxybenzoic acid) and normal saline (0.9% w/v aqueous NaCl) at various concentrations (0.001–0.010) m and temperature (T= 300.15–315.15) K. To understand the various possible molecular interactions, volumetric, acoustic, conductometric and viscometric parameters were evaluated using experimental measured values of densities (ρ), ultrasonic velocities (u), specific conductance (κ), and viscosities (η). The results derived from these parameters have been examined in terms of drug–solvent and drug-drug interactions. The results of physicochemical studies indicate that aspirin exhibits strong interactional and structure–forming behaviour in normal saline. These results were well supported by UV-visible spectral studies which indicate the existence of intense aspirin–normal saline interactions in the form of modification in absorption maximum and absorption wavelength. The cyclic voltammetric studies were also performed to explore the oxidation/reduction behaviour and effect of aspirin on hemolysis. The experimental analysis of these studies provides valuable insights for better drug design, drug delivery, compatibility, potential safety, and biological relevance for the pharmaceutical and health industries.

Study on solubility and solvation thermodynamics for the advancement of biorelevant activities of l-isoleucine and l-serine in aqueous ammonium chloride solutions in the temperature range of 288.15–308.15 K

This study investigated the dissolution behavior of l-isoleucine and l-serine in an aqueous salt solution (ammonium chloride), examining how variations in temperature and electrolyte concentration affect their solubility. We conducted careful experiments and used mathematical calculations to explore interactions at a molecular level. We observed that the structure of these amino acids and salt concentration in the aqueous medium influence their interactions, which affects dissolution. In the presence of electrolytes, l-isoleucine demonstrated a salting-out effect whereas l-serine showed a salting-in effect. This work examines the solute–solvent interactions of these solutes in aqueous ammonium chloride solutions. l-isoleucine exhibits a nonspontaneous reaction with increasing salt concentrations whereas l-serine shows spontaneous behavior. Gibbs free energy analysis revealed greater stability of l-serine. The pH and conductance measurements showed how these factors influence solution properties. This insight helps us comprehend the nature and behavior of these molecules in different situations, which could be helpful in drug formulation or protein purification in the future.

Oiling out and solubility measurement, molecular simulation and thermodynamic properties of d-tagatose in four aqueous binary solvent systems at 283.15 to 323.15 K

Solubility of D-Tagatose in four aqueous binary solvent systems from 278.15 K to 323.15 K was determined using the anti-solvent assisted gravimetric method. The solubility increases with temperature in all four binary solvents, with water, a good solvent, exhibiting a similar trend. In addition, the dissolution process generally follows the ’like dissolves like’ rule. The study indicates that the oiling out occurs when water exhibits a high molar fraction in water + 1-propanol, and water + isopropanol. Furthermore, we study the charge of the molecule using the molecular electrostatic potential surface (MEPS), aiming to analyze the molecular interactions. Then, to explain the dissolution behaviors of D-tagatose, the radial distribution function (RDF) by molecular dynamics simulations (MD) revealed a strong correlation between solute–solvent interactions and solubility, with significant solvent–solvent interactions. The solubility data was correlated using the modified Apelblat equation, Van’t Hoff equation, λh equation, and Jouyban-Acree model, with demonstrating the high consistency in the data. Finally, the thermodynamic properties revealed that the dissolution process of D-Tagatose is endothermic, and entropy-driven based on all positive values for ΔsolHo, ΔsolSo, ΔsolGo.

Quantitative Macromolecular Modeling Assay of Biopolymer-Based Hydrogels

The rubber elasticity theory has been lengthily applied to several polymeric hydrogel substances and upgraded from idealistic models to consider imperfections in the polymer network. The theory relies solely on hyperelastic material models in order to provide a description of the elastic polymer network. While this is also applicable to polymer gels, such hydrogels are rather characterized by their water content and visco-elastic mechanical properties. In this work, we applied rubber elasticity constitutive models through hyperelastic parameter identification of hydrogels based on their stress–strain response to compression. We further performed swelling experiments and determined the intrinsic properties, i.e., density, of the specimens and their components. Additionally, we estimated their equilibrium swelling and employed it in the swelling-equilibrium theory in order to determine the polymer–solvent interaction parameter of each hydrogel with regard to cross-linking. Our results show that the average mesh size obtained from the rubber elasticity theory can be regarded as a concentration-dependent characteristic length of the hydrogel’s network and couples the non-linear elastic response to the specimens’ inherent visco-elasticity through hysteresis as a quantifier of energy dissipation under large deformation.

Ceramic Microsphere Aerogels by Curled Precursor Molecular Chain: Antishrinkage, Thermal Insulation and Multiscale Simulations.

Ceramic aerogels prepared by the route of polymer-derived ceramics (PDCs) have been of significant attention in high-temperature insulation. However, the application of ceramic aerogels was seriously confined due to the structural damage and shrinkage cracking of ceramic precursors during pyrolysis. In this investigation, precursor ceramic microsphere aerogels with outstanding antishrinkage properties were prepared by storing strain in curled molecular chains and using polysilazane (PSZ) as the precursor. Meanwhile, precursor ceramic microsphere aerogels with different curled molecular chain structures were prepared by modulating solvent interactions and cross-linked structures. Different curled molecular chain structures were formed, and the impact on the antishrinkage properties of precursor aerogels was analyzed. The shrinkage resistance, thermal insulation, and mechanical properties of the prepared aerogels were tested and compared. Furthermore, the mechanism of the impact of different curled molecular chain structures on thermal insulation and mechanical properties was investigated through multiscale simulations combined with fractal theory. The thermal and stress transfer at the interfaces of different microsphere skeleton structures and the mechanisms were investigated. An idea for solving the problem of pyrolytic shrinkage in the preparation of ceramic aerogels was provided in this investigation. In addition, insights into the influence of the microsphere skeleton structure on the thermal and mechanical properties of ceramic aerogels were provided.

Solubility of letrozole in eight pure and five mixed solvents: Measurement, thermodynamic and molecular simulation analysis

In this work, the solubility of letrozole within eight single and five binary solvents was first systematically investigated at 283.15 K to 323.15 K via the gravimetric method. Subsequently, four thermodynamics formulas including modified Apelblat, λh, GSM and Jouyban-Acree were utilized to link the experimental outcomes of letrozole, all models achieved the good fitting performance and the ARD% was less than 2 %. The dissolvability of letrozole in chosen solvents exhibited a positive correlation with temperature, and co-solvency was observed in such mixed solvent systems as ethyl acetate + 1-propanol, and acetonitrile + 1-propanol. Furthermore, the sites of hydrogen bonding donor and acceptor of letrozole and solvents were analyzed through the molecular electrostatic potential surfaces (MEPs). Then solvent effect, solvation free energy and radial distribution function (RDF) analysis gained via molecular simulation were utilized to illuminate experimental phenomena, the outcomes manifested the polarity, cohesive energy density and other properties of solvents along with both solvent–solvent and solute–solvent interactions contributed differently to the dissolution processes. In the end, the apparent thermodynamic identities concerning letrozole within chosen solvent systems were computed under the van’t Hoff and Gibbs formulas, and outcomes showed that dissolution concerning letrozole was a procedure of endothermic and entropy mainly driven.

Organic Cationic-Coordinated Perfluoropolymer Electrolytes with Strong Li+-Solvent Interaction for Solid State Li-Metal Batteries.

The practical application of solid-state polymer lithium-metal batteries (LMBs) is plagued by the inferior ionic conductivity of the applied polymer electrolytes (PEs), which is caused by the coupling of ion transport with the motion of polymer segments. Here, solvated molecules based on ionic liquid and lithium salt with strong Li+-solvent interaction are inserted into an elaborately engineered perfluoropolymer electrolyte via ionic dipole interaction, extensively facilitating Li+ transport and improving mechanical properties. The intensified formation of solvation structures of contact ion pairs and ionic aggregates, as well as the strong electron-withdrawal properties of the F atoms in perfluoropolymers, give the PE high electrochemical stability and excellent interfacial stability. As a result, Li||Li symmetric cells demonstrate a lifetime of 2500 h and an exceptionally high critical current density above 2.3 mA cm-2, Li||LiFePO4 batteries exhibit consistent cycling for 550 cycles at 10 C, and Li||uncoated LiNi0.8Co0.1Mn0.1O2 cells achieve 1000 cycles at 0.5 C with an average Coulombic efficiency of 98.45 %, one of the best results reported to date based on PEs. Our discovery sheds fresh light on the targeted synergistic regulation of the electro-chemo-mechanical properties of PEs to extend the cycle life of LMBs.

Electrolyte Reconfiguration by Cation/Anion Cross‐coordination for Highly Reversible and Facile Sodium Storage

Hard carbon (HC) materials are promising anodes for sodium‐ion batteries (SIBs) owing to low cost, high specific capacity and low working potential. However, the poor compatibility of the electrolyte with HC leads to low initial coulombic efficiency (ICE) and sluggish Na+ transport kinetics. Here, we propose an electrolyte reconfiguration strategy based on the hard and soft acid and base (HSAB) theory by introducing methyltriphenylphosphonium bromide (MTPPB). MTPPB can realize a spontaneous cross‐coordination solvation structure with NaPF6 by selective affinity, synchronously optimizing the interfacial chemistry and sodium storage process. The advantages of the chemical π‐π bridging of MTPP+‐HC and interaction of MTPP+‐PF6− contribute to preferential and oriented reduction of PF6−, forming a low‐resistance supramolecular SEI. Additionally, Na+‐Br− coordination weakens the Na+‐solvent interactions, facilitating Na+ de‐solvation kinetics. Consequently, the HC||Na cell achieves a superior ICE of 96.6%, desirable rate capability under 25 °C and invisible capacity decay after 500 cycles at 1 C under −20 °C. The Na4Fe3(PO4)2P2O7||HC pouch battery displays a high ICE of 90.3% and a 15% increment of energy density under 25 °C. This work provides a guidance through electrolyte reconfiguration engineering for designing practical HC‐based SIBs with high energy/power density and long‐life span in the extended operating‐temperature range.

Electrolyte Reconfiguration by Cation/Anion Cross-coordination for Highly Reversible and Facile Sodium Storage.

Hard carbon (HC) materials are promising anodes for sodium-ion batteries (SIBs) owing to low cost, high specific capacity and low working potential. However, the poor compatibility of the electrolyte with HC leads to low initial coulombic efficiency (ICE) and sluggish Na+ transport kinetics. Here, we propose an electrolyte reconfiguration strategy based on the hard and soft acid and base (HSAB) theory by introducing methyltriphenylphosphonium bromide (MTPPB). MTPPB can realize a spontaneous cross-coordination solvation structure with NaPF6 by selective affinity, synchronously optimizing the interfacial chemistry and sodium storage process. The advantages of the chemical π-π bridging of MTPP+-HC and interaction of MTPP+-PF6- contribute to preferential and oriented reduction of PF6-, forming a low-resistance supramolecular SEI. Additionally, Na+-Br- coordination weakens the Na+-solvent interactions, facilitating Na+ de-solvation kinetics. Consequently, the HC||Na cell achieves a superior ICE of 96.6%, desirable rate capability under 25 °C and invisible capacity decay after 500 cycles at 1 C under -20 °C. The Na4Fe3(PO4)2P2O7||HC pouch battery displays a high ICE of 90.3% and a 15% increment of energy density under 25 °C. This work provides a guidance through electrolyte reconfiguration engineering for designing practical HC-based SIBs with high energy/power density and long-life span in the extended operating-temperature range.

General and Modular Synthesis of Covalent Organic Cages for Efficient Molecular Recognition.

Cage-type structures based on coordination and dynamic covalent chemistry have the characteristics of facile and efficient preparation but poor stability. Chemically stable organic cages, generally involving fragment coupling and multi-step reactions, are relatively difficult to synthesize. Herein, we offer a general and modular strategy to customize covalent organic cages with diverse skeletons and sizes. First, one skeleton (S) module with three extension (E) modules and three reaction (R) modules are connected by one- or two-step coupling to get the triangular monomer bearing three reaction sites. Then one-pot Friedel-Crafts condensation of the monomer and linking module of paraformaldehyde produces the designed organic cages. The cage forming could be regulated by the geometrical configuration of monomeric blocks. The S-E-R angles in the monomer is crucial; only 120° (2,4-dimethoxyphen as reaction module) or 60° (2,5-dimethoxyphen as reaction module) angle between S-E-R successfully affords the resulting cages. By the rational design of the three modules, a series of organic cages have been constructed. In addition, the host-guest properties show that the representative cages could strongly encapsulate neutral aromatic diimide guests driven by solvophobic interactions in polar solvents, giving the highest association constant of (2.58±0.18)×105 M-1.

General and Modular Synthesis of Covalent Organic Cages for Efficient Molecular Recognition

AbstractCage‐type structures based on coordination and dynamic covalent chemistry have the characteristics of facile and efficient preparation but poor stability. Chemically stable organic cages, generally involving fragment coupling and multi‐step reactions, are relatively difficult to synthesize. Herein, we offer a general and modular strategy to customize covalent organic cages with diverse skeletons and sizes. First, one skeleton (S) module with three extension (E) modules and three reaction (R) modules are connected by one‐ or two‐step coupling to get the triangular monomer bearing three reaction sites. Then one‐pot Friedel‐Crafts condensation of the monomer and linking module of paraformaldehyde produces the designed organic cages. The cage forming could be regulated by the geometrical configuration of monomeric blocks. The S−E−R angles in the monomer is crucial; only 120° (2,4‐dimethoxyphen as reaction module) or 60° (2,5‐dimethoxyphen as reaction module) angle between S−E−R successfully affords the resulting cages. By the rational design of the three modules, a series of organic cages have been constructed. In addition, the host‐guest properties show that the representative cages could strongly encapsulate neutral aromatic diimide guests driven by solvophobic interactions in polar solvents, giving the highest association constant of (2.58±0.18)×105 M−1.

Development of zeolite 5A-incorporated polyvinyl alcohol membrane for desalination by pervaporation

Abstract With the rapid depletion of potable and useable water resources globally due to population growth and the effects of global warming, the desalination of seawater – the world’s largest source of water – to acceptable quality levels is critical to meeting future water needs. This study investigates the use of zeolite 5A-incorporated polyvinyl alcohol membranes to produce fresh water from seawater for industrial and domestic use and evaluates the application of the pervaporation process on the separation performance. Polyvinyl alcohol and polyvinyl alcohol/zeolite 5A mixed matrix membranes were prepared by solution-casting technique, and their morphological, structural, and mechanical properties were analyzed by field emission scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and tensile strength tests. The swelling behavior and pervaporation performance of the membranes were investigated at different temperatures (30, 45, and 60 °C) using synthetic seawater containing 35 g L−1 NaCl, and membrane–solvent interactions were determined using data from sorption experiments. The membrane produced water flux and salt rejection values at 60 °C of 5.82 kg m−2 h−1 and >99.9 %, respectively.

Regulating Anode-Electrolyte Interphasial Reactions by Zwitterionic Binder Chemistry in Lithium-Ion Batteries with High-Nickel Layered Oxide Cathodes and Silicon-Graphite Anodes.

The practical application of silicon (Si)-based anodes faces challenges due to severe structural and interphasial degradations. These challenges are exacerbated in lithium-ion batteries (LIBs) employing Si-based anodes with high-nickel layered oxide cathodes, as significant transition-metal crossover catalyzes serious parasitic side reactions, leading to faster cell failure. While enhancing the mechanical properties of polymer binders has been acknowledged as an effective means of improving solid-electrolyte interphase (SEI) stability on Si-based anodes, an in-depth understanding of how the binder chemistry influences the SEI is lacking. Herein, a zwitterionic binder with an ability to manipulate the chemical composition and spatial distribution of the SEI layer is designed for Si-based anodes. It is evidenced that the electrically charged microenvironment created by the zwitterionic species alters the solvation environment on the Si-based anode, featuring rich anions and weakened Li+-solvent interactions. Such a binder-regulated solvation environment induces a thin, uniform, robust SEI on Si-based anodes, which is found to be the key to withstanding transition-metal deposition and minimizing their detrimental impact on catalyzing electrolyte decomposition and devitalizing bulk Si. As a result, albeit possessing comparable mechanical properties to those of commercial binders, the zwitterionic binder enables superior cycling performances in high-energy-density LIBs under demanding operating conditions.

Cost-Effective Acetonitrile-Based Precursor Solution Mitigates Heterogeneous Nucleation for Efficient and Stable Perovskite Solar Cells.

Solution-processing is the primary method for fabricating high-efficiency perovskite solar cells (PSCs), where solvent choice critically influences film formation and quality. Although additives can optimize film formation dynamics by balancing nucleation and growth of perovskite, they can also induce heterogeneous nucleation due to competitive coordination and varying crystallization kinetics, leading to compositional heterogeneity and structural disorders. Herein, a perovskite precursor solution is developed using acetonitrile (ACN) as a weak coordination host solvent instead of the traditional N,N-dimethylformamide (DMF). The ACN-based perovskite precursor solution reduces heterogeneous nucleation typically caused by the competitive coordination effect of DMF, and cuts costs by half compared to DMF-based precursor solutions. This approach promotes a single crystallization pathway via a dimethyl sulfoxide-solvated intermediate phase to α-FAPbI3, which extends the anti-solvent operation window, and enhances the crystallinity of perovskite films, and reduces defect states. The power conversion efficiencies (PCE) of 23.62% and 20.13% is achieved for the PSC and minimodule, respectively. The PSC retains over 97% of its initial efficiency after 800h of continuous illumination under maximum power point tracking (MPPT). These findings provide valuable insights into solvent interactions in perovskite film formation and offer a cost-effective strategy for improving the device's performance and stability.

Role of Intermolecular Interactions in Deep Eutectic Solvents for CO2 Capture: Vibrational Spectroscopy and Quantum Chemical Studies.

Recent research and reviews on CO2 capture methods, along with advancements in industry, have highlighted high costs and energy-intensive nature as the primary limitations of conventional direct air capture and storage (DACS) methods. In response to these challenges, deep eutectic solvents (DESs) have emerged as promising absorbents due to their scalability, selectivity, and lower environmental impact compared to other absorbents. However, the molecular origins of their enhanced thermal stability and selectivity for DAC applications have not been explored before. Therefore, the current study focuses on a comprehensive investigation into the molecular interactions within an alkaline DES composed of potassium hydroxide (KOH) and ethylene glycol (EG). Combining Fourier transform infrared (FT-IR) and quantum chemical calculations, the study reports structural changes and intermolecular interactions induced in EG upon addition of KOH and its implications on CO2 capture. Experimental and computational spectroscopic studies confirm the presence of noncovalent interactions (hydrogen bonds) within both EG and the KOH-EG system and point to the aggregation of ions at higher KOH concentrations. Additionally, molecular electrostatic potential (MESP) surface analysis, natural bond orbital (NBO) analysis, quantum theory of atoms-in-molecules (QTAIM) analysis, and reduced density gradient-noncovalent interaction (RDG-NCI) plot analysis elucidate changes in polarizability, charge distribution, hydrogen bond types, noncovalent interactions, and interaction strengths, respectively. Evaluation of explicit and hybrid models assesses their effectiveness in representing intermolecular interactions. This research enhances our understanding of molecular interactions in the KOH-EG system, which are essential for both the absorption and desorption of CO2. The study also aids in predicting and selecting DES components, optimizing their ratios with salts, and fine-tuning the properties of similar solvents and salts for enhanced CO2 capture efficiency.

Estimation of Electric Dipole Moment by Solvatochromism, Computational Method, and Study of the Effect of Solvents by Preferential Solvation of 6 - Methoxy-4-(4-Nitro-Phenoxy Methyl)-Chromen-2-One (6mnpm).

At room temperature, the absorption and fluorescence properties of coumarin 6-Methoxy-4-(4-nitro-phenoxy methyl)-chromen-2-one (6MNPM) are investigated in pure organic solvents and a combination of acetonitrile (ACN) and tetrahydrofuran (THF). The pure solvents' influence on spectral characteristics is examined by applying theories such as Kamlet and Catalan's multiple linear regression techniques, Reichardt's microscopic solvent polarity parameter, and the Lippert-Mataga polarity function. The significant role of solute-solvent interactions in pure solvents, particularly dielectric interaction and hydrogen bonding. However, hydrogen bonding interactions dominate the contribution of dielectric interactions. The electric dipole moments of both the ground as well as excited states had been calculated using the Solvatochromic method. The value of the excited state electric dipole moment and the redshifts of the emission spectra show that the emitting singlet state has an intramolecular charge transfer (ICT) character. From Catalan's linear regression, we found that di-polarity has a much smaller influence than polarizability. By solvation study, we conclude that Tetrahydrofuran solvent is preferred over Acetonitrile.

How does the integration of amino acids enhance the bonding ability of triazine-based inhibitors with iron surfaces: Insights from SCC-DFTB, COSMO-RS and molecular dynamics simulations

Theoretical investigations into the adsorption of molecules on metal surfaces play a pivotal role in the development of more efficient corrosion inhibitors. This study offers a novel approach by combining Density Functional Tight Binding (DFTB), Molecular Dynamics (MD) simulations, and conductor-like screening model for realistic solvation (COSMO-RS) calculations to comprehensively assess the interaction and diffusion properties of glycine (Gly), 2,2′-azanediyldiacetic acid (IDA), and 5-aminopentanoic acid (5-APA) with two 1,3,5-triazine (Tris) derivatives (Tris-Gly and Tris-IDA) for corrosion protection of carbon steel in acidic medium. The solvation properties of these molecules were evaluated alongside their interaction strength with the Fe(1 1 0) surface, considering both neutral and protonated forms. DFTB simulations revealed a clear trend in interaction energies, following the order: Tris-IDA > Tris-Gly > 5-APA > IDA > Gly. It ranges from −1.191 eV to −1.853 eV, with the highest stability observed for protonated Tris-IDA (−1.853 eV), while neutral Glycine exhibits the lowest interaction energy (−1.263 eV). While these theoretical results diverged slightly from experimental observations, with Tris-Gly outperforming Tris-IDA, this discrepancy was attributed to steric effects and solvent interactions. The DFTB results also indicated strong covalent interactions, particularly involving acetic groups, between the inhibitors’ orbitals and the iron’s 3d orbitals. MD simulations further demonstrated the impact of protonation on inhibitor mobility, with reduced diffusion coefficients due to enhanced electrostatic interactions and hydrogen bonding. COSMO-RS solvation analysis confirmed the strong hydrogen bonding capabilities of these molecules with water. Overall, this study elucidates the mechanisms of corrosion inhibition by integrating multiple simulation techniques, providing key molecular insights that can guide the design of more effective corrosion inhibitors. The findings emphasize the significance of electronic interactions and molecular structure in enhancing inhibitor performance, making this a valuable contribution to corrosion science.