Non-bonded Energy Research Articles

Effects of Cross-Linking Degree and Characteristic Components on Mechanical Properties of Highly Cross-Linked Phenolic Resins: A Molecular Dynamics Simulation Study

Phenolic resins (PF), naphthol modified phenolic resins (NPF), and cyanate ester modified phenolic resins (CEPF) were constructed where naphthols and triazine rings act as chain reinforcing and chain-to-chain bridging roles, respectively. Then, molecular dynamics simulations were performed to predict the Young’s modulus. The results show that methylene bridges and branched phenolic rings are key factors affecting the stiffness of resin. Introducing naphthols does not provide a clear benefit in stiffness due to a counterbalance between the rise in nonbonded energies and the drop in methylene bridges. For CEPF, the chain-to-chain bridges of triazine rings increase the Young’s modulus up to 2.93 GPa and contribute significantly to stiffness compared to reinforcing chains by rigid naphthols. The trend of the three systems from plastic to the cured state can be seen in the mean squared displacement and Young’s modulus. These findings can support the study of the molecular design of PF to optimize stiffness.

Experimental and molecular dynamics study of fuel desulfurization process using deep eutectic solvent

The sulfur-containing compounds in China's crude oil mainly exist in the form of thiophene (TPs). More than 80% of TPs are composed of dibenzothiophene (DBT). The combustion of sulfur-containing fuel oil pollutes the air. Studies have shown that DES, as a new solvent similar to ionic liquids, has the advantages of simple preparation, easy availability of raw materials and high extraction rate. In this paper, experiments on DES synthesis were carried out to screen DES with the best extraction efficiency, and the effects of extraction operation temperature and initial sulfur concentration of raw oil on DES extraction and desulfurization were explored. The DES separation mechanism for DBT extraction from n-heptane-DBT was used as the simulated oil. Quantum chemistry was calculated for 9 commonly used DES, and the hydrogen bonding between DES-DET-n-heptane was analyzed by using the obtained σ-Profiles map information, and the selected DES was compared with the auxiliary experiment from the perspective of quantum chemistry. Then, the molecular dynamics (MD) simulation between different DES and raw oil was carried out, that is, the non-bond interaction energy, radial distribution function, spatial distribution function and mean square shift results of DBT-Heptane-DES calculated by molecular dynamics were used to deeply analyze the microscopic separation mechanism of DES extraction desulfurization. The results show that the DES composed of choline chloride/diethylene glycol can theoretically perform more efficient desulfurization operations, and this theoretical analysis method can provide a strong basis for the desulfurization of other types of DES and the separation of other systems.

Influence of Polar Protic Solvents on Urea Morphology: A Combination of Experimental and Molecular Modeling

The modification of crystal shapes is used intensively in designing particles with desired properties to ensure the efficiency of the manufacturing processes. In this work, urea crystals grew in various polar protic solvents by cooling crystallization that produced α-form urea. The aspect ratios of the crystals were found to be in the range from 14.77 to 1.44, grown in the following solvents: water > methanol > ethanol > isopentanol > isobutanol > pentanol > butanol > propanol > isopropanol. An attempt to establish a correlation between the nonbonded energy, solvent molecule size, binding energy, and the change in morphology revealed that the aforementioned factors could not accurately predict the aspect ratios of the urea crystals. The solvent-surface binding energy showed the {111} and {001} capping facets recorded the highest strength (most negative energy), while the {110} facet was the lowest. The inhibition of the solvent molecules on the {001} and polar {111} facets stopped the growth along the c-axis by stopping the formation of synthon A and synthon B, while the growth along the a-axis was halted by stopping the formation of synthon B. The transformation from elongated cuboid to prismoidal shape of urea was governed by the {111}/{110} energy ratio, i.e., it must be <1.78.

Experimental and theoretical study on molecular structure construction of Hongliulin coal

A suitable model can reflect the properties of coal well. In this study, the properties of HongLiuLin (HLL) coal were studied through industrial analysis, XPS, 13C NMR and FTIR. The results show the coal has middle-rank bituminous coal characteristics, and the ratio of aromatic bridge carbon to aromatic peripheral carbon is 0.16. Benzene and naphthalene ring are the main components of the aromatic structure. N and S exist in pyrrole nitrogen and fatty sulfur, respectively. The hypothesis method was used to deduce the molecular formula C130H73O21NS of the coal model. The stability of the carbon skeleton was improved through the Van Der Waals (VDW) forces in non-bonding energy. Verification of NMR, FTIR and density was completed based on quantum chemistry and molecular mechanics. The coal model energy level orbitals analysis shows that the LUMO and HOMO orbitals are located in the aromatic functional groups. This work provides a reference for further research on the nature of coal in north Shaanxi and improving the utilization rate of coal.

Inhibitory action of indanone-carbamate hybrid molecules on the aggregation of Aβ16−22 peptides and their translocation across POPC lipid bilayer

The aggregation of Aβ peptides leads to Alzheimer's Disease (AD), the most common kind of dementia. This neurodegenerative disease has no permanent cure to date. Drug design for Alzheimer's is, therefore, a major challenge to the scientific community. A recent experimental study showed the potency of two indanone-carbamate-based molecules to act as drugs against AD. However, the central molecular mechanism of action of these inhibitors is unknown. For knowing the mechanism of amyloid aggregation and the role of these novel molecules as inhibitors, an extensive all-atom molecular dynamics simulation of the Aβ16−22 peptides is performed. A variety of analyses are carried out to explore the structural change of the peptides in an aqueous medium in the absence and presence of inhibitors viz. secondary structure analysis, solvent accessible surface area calculation, residue-wise and Cα atom-wise contact mapping. In order to identify the peptide's residues associated with amyloid aggregation and interaction with the inhibitor, nonbonding interaction energies, radial distribution functions, coordination number, hydrogen bonds, and potential of mean forces are estimated. The central hydrophobic core, more importantly, the aromatic phenylalanine residues are found to play a substantial role in the formation of toxic amyloid oligomers. All the analyses demonstrate diminishing interpeptide interactions in presence of the inhibitors thereby checking amyloid aggregation. The molecules are also found to destabilize preformed amyloid fibrils. Furthermore, permeation properties of these small molecule inhibitors are investigated across a model POPC lipid bilayer, revealing their biocompatibility and translocation mechanisms.

CO2 capture with green ionic liquid and deep eutectic solvent: A comparative study

Increasing the greenhouse gases in the atmosphere, mainly from human activities leads to the global warming phenomenon and poses a serious threat to life on the earth.Hence, there is a pressing need to mitigate greenhouse gases emission and overcome global warming. It is proven that Ionic liquids (ILs) and deep eutectic solvents (DESs) are fruitful materials to capture gases and reduce their emission. Here, we investigate the environmentally friendly and cost-effective cholinium geranate ([Cho][Ger]) IL and cholinium geranate:geranic acid ([Cho][Ger]:Ger acid) DES, for carbon dioxide (CO2) capture. To this end, the density functional theory (DFT) and molecular dynamics (MD) simulation approaches are employed to provide quantitative microscopic insight into the interactions between CO2 and IL/DES. The adsorption energies of IL…CO2 and DES…CO2 are explored through the DFT calculations and show stronger interaction between the IL…CO2 than DES…CO2. The MD simulation analyses including density profile, non-bonded energy, radial distribution function (RDF), and spatial distribution function (SDF) affirm the stronger interaction between the IL…CO2 than DES…CO2. Meanwhile, the DFT and MD simulation results reveal the strongest interaction between CO2 and [Ger] - anion of both IL and DES. Furthermore, the minimum potential of mean force (PMF) of CO2 at the IL-air interface represents the favorable adsorption of CO2 on IL. Overall, our molecular level findings which are not accessible through the experimental approaches could help experimentalists find high-efficient solvents for CO2 capture.

Prediction of co-amorphous formation using non-bonded interaction energy: Molecular dynamic simulation and experimental validation

Co-amorphous (CA) formulation is a promising strategy to improve the solubility of poorly water-soluble drugs, however, effective prediction of a CA system is a challenge. In this study, a modified non-bonded interaction energy (ΔEnon-bonded) model was developed based on 105 solvent-based cases of 13 drugs chosen from the literature to predict CA formation by solvent-based methods using molecular dynamic simulation. With the cut-off value of −3500 kJ·mol−1, the model hit 5 gefitinib CAs and 4 erlotinib CAs, validating its feasibility. The quadratic relationship between co-former proportion (xco-former) and ΔEnon-bonded was analyzed using polynomial regression, indicating the xco-former is most likely to render CA when ΔEnon-bonded reaches its extreme value. Hydrogen bonds between the NH group of active pharmaceutical ingredient and sulfonamide group of co-former were confirmed experimentally and computationally. Typical CA samples showed remarkable improved solubility (12.1 and 9.3 times) in PBS solution and good physical stability under room conditions.

Atomic insight into the nano-cracking resistance and interfacial bonding mechanism of carbon nanotube reinforced bitumen

Bitumen reinforced with carbon nanotubes (CNTs) exhibits excellent mechanical performance in pavement engineering. However, its nanoscale enhancement mechanisms have not yet been studied. This study utilizes molecular dynamics (MD) simulation to investigate the effects of CNTs on the load-induced cracking process in bitumen and elucidate fundamental insights into the interaction mechanism between the bitumen-CNT interface. The simulation results demonstrate that the aromatic rings in bitumen molecules can interact with the sp2 carbon system of CNTs through π–π stacking, which enhances the load transfer efficiency and mechanical performance of bitumen. During the cracking process, the connected CNTs can bridge the nano-cracks, elongate the propagation path, and increase the overall fracture resistance. Moreover, the analysis of the energy contribution reveals that the pulling-out effect of CNTs can significantly increase their capacity to absorb external energy and save it as the non-bonded energy of the bitumen system, which results in a greater tolerance under external loading. However, debonding and sliding of the bitumen-CNT interface are observed during the cracking process, which weakens the interfacial bonding and reduces the strengthening effect. Future studies will be focused on improving the load-transfer efficiency at the interface to fully exploit the superior mechanical properties of CNTs.

Role of Strong Localized vs Weak Distributed Interactions in Disordered Protein Phase Separation.

Interaction strength and localization are critical parameters controlling the single-chain and condensed-state properties of intrinsically disordered proteins (IDPs). Here, we decipher these relationships using coarse-grained heteropolymers comprised of hydrophobic (H) and polar (P) monomers as model IDPs. We systematically vary the fraction of P monomers XP and employ two distinct particle-based models that include either strong localized attractions between only H-H pairs (HP model) or weak distributed attractions between both H-H and H-P pairs (HP+ model). To compare different sequences and models, we first carefully tune the attraction strength for all sequences to match the single-chain radius of gyration. Interestingly, we find that this procedure produces similar conformational ensembles, nonbonded potential energies, and chain-level dynamics for single chains of almost all sequences in both models, with some deviations for the HP model at large XP. However, we observe a surprisingly rich phase behavior for the sequences in both models that deviates from the expectation that similarity at the single-chain level will translate to a similar phase-separation propensity. Coexistence between dilute and dense phases is only observed up to a model-dependent XP, despite the presence of favorable interchain interactions, which we quantify using the second virial coefficient. Instead, the limited number of attractive sites (H monomers) leads to the self-assembly of finite-sized clusters of different sizes depending on XP. Our findings strongly suggest that models with distributed interactions favor the formation of liquid-like condensates over a much larger range of sequence compositions compared to models with localized interactions.

Rejuvenation effect of aged SBS-modified asphalt utilizing molecule analysis

The performance of styrene-butadiene-styrene modified asphalt (SBSMA) is significantly impacted by its aging and regeneration. In this research, the molecular dynamics simulation was utilized to investigate the rejuvenation effect of active reagents on aged SBS modified asphalt through the following tasks: 1) verifying the accuracy of the asphalt model by density and solubility parameters; 2) assessing the changes in the rejuvenated asphalt model's energetic parameters and volume parameters, 3) studying the interaction energy between SBS molecules and asphalt molecule models, and 4) evaluating the relative concentration, interfacial interaction energy, and diffusion effect of the asphalt-asphalt models. The results indicated that the restored broken SBS molecule substantially impacted the functionality of the rejuvenated asphalt binder. For Methylene-bis(4-cyclohexylisocyanate) (HMDI) and 1,6-Hexanediol Diglycidyl Ether (HDE) rejuvenated asphalts, the non-bond energy decreased gradually with the repair of broken SBS molecular structures. The free volume fraction of rejuvenated binders was lower than that of SBSMA, indicating that the compactness and packing degree of the rejuvenated asphalt were increased. The interaction energy between SBS and asphalt molecules in rejuvenated asphalt increased because of the enhanced van der Waals interaction between the reconstructed SBS molecule and rejuvenated binders. The free HDE molecular chain reduced the interaction energy between SBS and asphalt molecules. For the asphalt-asphalt models, the diffusion coefficient of the SBSMA-rejuvenated asphalt model was lower than that of the SBSMA-SBSMA model. The HDE rejuvenated asphalt showed better diffusion behavior than SBSMA, and SBS molecules repaired by HDE had excellent fluidity. The interfacial interaction energy of the SBSMA-rejuvenated asphalt model was higher than that of the SBSMA-SBSMA model. With the repair of the broken SBS molecular chain, the interfacial interaction energy between HMDI rejuvenated asphalt and SBSMA increased gradually. In contrast, the interfacial interaction energy between HDE rejuvenated asphalt and SBSMA decreased gradually. The fully restored SBS molecular structure had stable thermodynamic properties and could accelerate the diffusion effect of rejuvenated asphalt.

Revealing Mechanisms of Aging and Moisture on Thermodynamic Properties and Failure Patterns of Asphalt-Aggregate Interface from the Molecular Scale

The primary purpose of this study was to reveal the effect of aging and moisture on the failure behavior of asphalt binder–aggregate interfaces from thermodynamic properties and the molecular scale and to provide ideas for improving the service life and weather resistance of materials. A 12-component asphalt binder model, an oxidation-aged asphalt binder model, three types of aggregates (i.e., SiO2-, CaO-, and Al2O3-based) models, and corresponding confined asphalt-aggregate models in dry or wet conditions were developed using Materials Studio version 2019 software. Thermodynamic parameters that characterize interfacial failure behavior, including surface free energy, cohesive work, and adhesion work between asphalt binder (unaged and aged samples) and aggregates were obtained by molecular dynamics simulations. A pull-off test was simulated using molecular dynamics to analyze asphalt-aggregate failure patterns and mechanisms. Five tensile rates were applied in tensile simulations of asphalt-SiO2 aggregate, and bond strength at various temperatures was investigated. The findings suggested that oxidative aging reduces thermodynamic properties such as the surface free energy and cohesive energy of asphalt binders but enhances the potential and nonbond energy of asphalt binders. The ranking of the adhesion between unaged asphalt binder and various aggregates is as follows: SiO2>CaO>Al2O3. Oxidative aging has a distinct influence on the adhesion properties of the aforementioned asphalt binder–aggregate interfaces. Furthermore, outcomes for debonding energy and energy ratio (ER) value in the asphalt-CaO aggregate system exhibited the best water stability. Increasing tensile rate caused the failure patterns of the asphalt-aggregate mixes to change from adhesive failure damage between asphalt and aggregate to cohesive failure within the asphalt binder. Temperature had a nonnegligible impact on bond strength at the asphalt-aggregate interface.

Stiffening and Toughening of Asphalt Mastic Induced by Bitumen–Mineral Selective Molecular Adsorption and Nanostructural Reconstruction

Asphalt mastic is the most important binder in asphalt mixtures and its rheology is inevitably influenced by the mineral aggregates. Due to the little consideration that has been paid to aggregates’ effects, the rheological properties of mastic films have not been accurately characterized for the present method. Therefore, this study aimed to investigate the rheological characteristics of mastic affected by mineral aggregates and reveal its fundamental mechanism of interfacial interaction. The results suggest that the aggregates increased the stiffness and toughness of mastic within the linear and nonlinear viscoelastic regions. The mastic on limestone had a higher linear viscoelastic modulus than that on basalt below 35 °C, and its ratio reached up to 1.18. However, the modulus of the mastic on basalt surpassed that on limestone by over 50 °C, and the maximum ratio reached 2.17. The mastic in contact with the limestone had a higher failure strain and failure modulus than that in contact with the basalt, the ratios of which reached 1.60 and 1.32, respectively. The macrorheological characteristics are closely related to the nanostructures and intermolecular interactions of bitumen–mineral systems. The coexistence of a stable bitumen nanostructure and an adsorbed layer on the calcite substrate provided a strong bonding energy and high resistance to external shear deformation, leading to the high stiffness and toughness of the limestone. Abundant metal ions from augite and albite diffused into the bitumen layer and destroyed its nanostructure, decreasing the stability of the mastic–basalt interface system. The non-bond energy of bitumen-calcite was 14.15% higher than that of bitumen-albite, and the ratio of shear stress of the bitumen-calcite to the bitumen-albite reached up to 6.8. Therefore, the calcite in limestone reinforced the bitumen, and the augite and albite in basalt destroyed the bitumen colloidal structure. This provides a fundamental understanding of the rheological characterization of mastic on mineral aggregates.

Decoupling Planarizing and Steric Energetics to Accurately Model the Rigidity of π-Conjugated Polymers.

The π-conjugated backbone of semiconducting polymers gives rise to both their electronic properties and structural rigidity. However, current computational methods for understanding the rigidity of polymer chains fail in one crucial way. Namely, standard torsional scan (TS) methods do not satisfactorily capture the behavior of polymers exhibiting a high degree of steric hindrance. This deficiency in part stems from the method by which torsional scans decouple energy related to electron delocalization from that related to nonbonded interactions. These methods do so by applying classical corrections of the nonbonded energy to the quantum mechanical (QM) torsional profile for polymers that are highly sterically hindered. These large corrections to the energy from nonbonded interactions can substantially skew the calculated QM energies related to torsion, resulting in an inaccurate or imprecise estimation of the rigidity of a polymer. As a consequence, simulations of the morphology of a highly sterically hindered polymer using the TS method can be highly inaccurate. Here, we describe an alternative, generalizable method by which the delocalization energy can be decoupled from the energy associated with nonbonded interactions─the "isolation of delocalization energy" (DE) method. From torsional energy calculations, we find that the relative accuracy of the DE method is similar to the TS method (within 1 kJ/mol) for two model polymers (P3HT, PTB7) when compared to quantum mechanical calculations. However, the DE method significantly increased the relative accuracy for simulations of PNDI-T, a highly sterically hindered polymer (8.16 kJ/mol). Likewise, we show that comparison of the planarization energy (i.e., backbone rigidity) from torsional parameters is significantly more precise for both PTB7 and PNDI-T when using the DE method as opposed to the TS method. These differences affect the simulated morphology, with the DE method predicting a significantly more planar configuration of PNDI-T.

Molecular dynamics simulation of phosphatidylcholine membrane in low ionic strengths of sodium chloride

The one-microsecond molecular dynamics simulations of a membrane-protein complex investigate the influence of the aqueous sodium chloride solutions on the structure and dynamics of a palmitoyl-oleoyl-phosphatidylcholine bilayer membrane. The simulations were performed on five different concentrations (40, 150, 200, 300, and 400 mM) in addition to a salt-free system by using the charmm36 force field for all atoms. Four biophysical parameters, (membrane thicknesses of annular and bulk lipids, and the area per lipid of both leaflets), were computed separately. Nevertheless, the area per lipid was expressed by using the Voronoi algorithm. All time-independent analyses were carried out for the last 400 ns trajectories. Different concentrations revealed dissimilar membrane dynamics before equilibration. The biophysical properties of the membrane (thickness, area-per-lipid, and order parameter) have non-significant changes with increasing ionic strength, however, the 150 mM system had exceptional behavior. Sodium cations were dynamically penetrating the membrane forming weak coordinate bonds with single or multiple lipids. Nevertheless, the binding constant was unaffected by the cation concentration. The electrostatic and Van der Waals energies of lipid-lipid interactions were influenced by the ionic strength. On the other hand, the Fast Fourier Transform was performed to figure out the dynamics at the membrane-protein interface. The nonbonding energies of membrane-protein interactions and order parameters explained the differences in the synchronization pattern. All results were consensus with experimental and theoretical works.Communicated by Ramaswamy H. Sarma

Functionalization of Metal–Organic Framework Nanochannels for Water Transport and Purification

Artificial water nanochannels (AWCs) have drawn great attention due to their potential use in water purification. Herein, we propose an AWC design, which is based on coordinatively functionalizing unsaturated metal sites found in metal–organic frameworks (MOFs) with one-dimensional nanochannels. As a computational demonstration, we consider two MOFs, namely, Ni-CPO-27 and Ni-CPO-54, and graft proline, imidazolecarboxylic acid, imidazolecarboxaldehyde, pyrazolecarboxylic acid, and pyrazole carbaldehyde molecules into the MOF nanochannels. To assess the strength of the molecule-metal binding, binding energies were calculated using density functional theory. The results indicate that the MOFs containing either proline or 2-imidazolecarboxylic acid form water-stable AWCs with binding energies twice that of the binding energy of water. To shed light on the water diffusion mechanism in the proline-Ni-CPO-27/54 and 2-imidazolecarboxylic-Ni-CPO-27/54 AWCs, molecular dynamics simulations were performed to calculate the mean-squared displacement of water molecules and nonbonded interaction energies between select pairs of atoms in water and coordinated molecules were analyzed. It was found that the fastest water diffusion occurs in proline-Ni-CPO-54 with a self-diffusion coefficient of 7.2 ± 0.5 × 10–8 cm2/s. In comparison, the fastest water self-diffusion coefficient reported in a carbon nanotube-based AWC is 9 × 10–6 cm2/s. Nonbonded interactions between specific atom pairs regulate water diffusion in the functionalized MOF nanochannels. In particular, the change in water mean-squared displacement with changing water loading correlates well with the nonbonded energies between the partially positively charged hydrogen atoms in water and the partially negatively charged oxygen and nitrogen atoms in the proline and 2-imidazolecarboxylic acid molecules. The results presented herein indicate that water-stable MOFs could perform well as AWCs, thereby lending support to the further design and synthesis of MOF-based AWCs for water purification.

Effectiveness of the hydrophobic core of pyridine tethered N-acyl glycine micelles in improving chromenoquinoline synthesis in water

The organic transformations in water are considered a safe, non-toxic, economical, and eco-friendly alternative. A new series of amphiphile, N-acyl-N-(pyridin-2-ylmethyl)glycine (PyNAG) with variable hydrophobicity was successfully synthesized from glycine. The self-assembly properties were characterized by critical micellar concentration (CMC), aggregation number (Nagg), and diameter (DH). The PyNAG with N- stearoyl moiety showed lower CMC, higher Nagg, and larger DH compared to PyNAG with N- lauryl moiety. Molecular dynamics simulation reveals that the micelle structure is compact and non-bonded energy contribution arises from electrostatic, and van der Walls forces contribute to perfect packing and micelle formation. The ability of the PyNAG micelles to execute important organic transformations in water was demonstrated through synthesizing chromenoquinoline via the Povarov reaction. Micelles with varying diameters were used to conduct the Povarov reaction in order to better understand the functions of the hydrophobicity core of the micellar environment in organic reactions. The results reveal that the Povarov reaction produces a good yield in N-stearoyl-N-(pyridin-2-ylmethyl)glycine (PyN18G) micelles, better than organic solvent and commercial surfactant. Moreover, a linear correlation between the yield and the hydrophobicity of the PyNAG was observed. The findings demonstrate that the micellar interior significantly affects the reactivity of the substrate, which should be taken into consideration while creating new media for metal-catalyzed green synthesis.

Effect of Pressurized Hydrothermal Treatment on the Properties of Cellulose Amorphous Region Based on Molecular Dynamics Simulation

Based on Materials Studio software, a cellulose chain with a polymerization degree of 20 and several water molecules were constructed to form a cellulose amorphous region–water model. The effect of pressure on the wood properties during hydrothermal treatment was investigated to explain the changes in the macroscopic properties from a microscopic perspective, thus providing a theoretical basis for wood heat treatment research. In this study, we performed dynamic simulations at atmospheric pressure (0.1 MPa) and pressurized (0.2 MPa, 0.4 MPa, and 0.6 MPa) conditions under a combination of NPT. In addition, five aspects were analyzed in terms of energy change: cell parameters and density, cellulose mean square displacement, number of hydrogen bonds, and mechanical properties. The results showed that pressurized hydrothermal treatment increased the densification of the wood, decreased the volume, and increased the density. As the pressure increased, the difference between the average value of the nonbond energy and the total potential energy gradually decreased, the bond energy decreased, and the interatomic repulsive force within the molecule gradually weakened. The increase in the number of hydrogen bonds enhanced the restraining effect on the arrangement of cellulose molecular chains and slowed down the movement of the cellulose chains. Young’s modulus (E) and shear modulus (G) increased with increasing pressure, and Poisson’s ratio (γ) and K/G decreased with increasing pressure during the pressurized hydrothermal treatment of wood. The pressurized hydrothermal treatment increased the stiffness and decreased the toughness of the wood compared with those of the model with atmospheric pressure hydrothermal treatment.

Atomistic study on thermo-mechanical behavior and structural anisotropy of montmorillonite under triaxial tension and compression

The macroscopic thermo-mechanical behavior and structural anisotropy of swelling clay are mainly driven by the local deformation and failure of clay particles in nanoscale. Microscopic thermo-mechanical behavior of clay particles is rarely explored under triaxial compression and tension with constant mean stress. In this work, the effect of temperature on the mechanical behavior and structural anisotropy of montmorillonite under the above loading paths in the parallel (x- and y-) and perpendicular (z-) directions to crystal layers, has been investigated using Molecular Dynamic (MD) simulations. The obtained stress-strain response showed that the higher the temperature, the lower the absolute value of peak differential stress and peak strain. In terms of overall peak stress (axial or radial stress), the resistance of montmorillonite to compression deformation was greater than that to tension. Furthermore, the sequence of peak differential stress in three directions was y > x > z at 200–500 K and y > z > x at 700–900 K for tension, while z > y > x at all temperatures for compression. The deformation mechanism of montmorillonite was mainly driven by the collapse of the clay mineral layers or bending deformation, determined by different loading paths and directions. The bond-breakage of montmorillonite structure was determined, showing the structural anisotropy of clay particles. The higher the temperature, the earlier the bond-breakage, and the greater the deformation of montmorillonite. The evolution of various types of energy with strain was obtained during the failure process, where the energy of montmorillonite was dissipated via changes in position between atom pairs, mainly showing changes in non-bond energy.

Decontamination of enoxacin containing aqueous phase through hydrophobic deep eutectic solvents: Solvent regeneration and quantum chemical insights

The current work addresses the extraction of a drug (enoxacin) from an aqueous environment by liquid-liquid extraction using three hydrophobic deep eutectic solvents (DES) namely, (a) dl-menthol: decanoic acid (1:1), (b) dl-menthol: dodecanoic acid (2:1), and (c) dodecanoic acid: decanoic acid (1:2). The experiments were conducted at varying mass ratios of DES/ water phase at ambient condition followed by quantum chemical (QC) analysis. Within the batch process with a single cycle, the extraction efficiency and the distribution ratio of 82 % and 4.75 respectively, were reported with the DES; dl-menthol: decanoic acid (1:1). Different initial drug concentrations (5 to 20 ppm) were introduced to observe the extraction performance at various contamination levels. Followed by the batch-type extraction experiments, three different recycling schemes have been implemented to assess the reuse and recovery of DESs. A 90 % percentage extraction was achieved by recycling the DES phase with purification through activated carbon (AC) which allowed it to maintain its continuity of the aqueous phase. The higher hydrophobicity of the DES phase with relatively high drug solubility proved to be the driving force of the enhanced DES-drug interaction. This was supported by the QC analysis as comparably higher non-bonded interaction energy was obtained for the DES-enoxacin complex suggesting stronger interaction and compactness. The charge transfer (CT) process confirmed the magnitude of charge transfer between DES and the drug through natural bonding orbital (NBO) charge analysis. Non-bonded interactions with dispersion effect were confirmed by the structural arrangement analysis of the complex supported by frontier molecular orbital (FMO) analysis. The quantum theory of atom in molecules and the non covalent interaction (QTAIM & NCI) analysis suggest hydrogen bonding and dispersion interactions (van der Waals) as the basis of interaction between the molecular groups.

Assessment of the properties of natural-based chiral deep eutectic solvents for chiral drug separation: insights from molecular dynamics simulation.

The structural and physicochemical properties of chiral deep eutectic solvents (DESs) consisting of racemic mixtures of menthol and acetic acid (DES1), racemic mixtures of menthol and lauric acid (DES2), and racemic mixtures of menthol and pyruvic acid (DES3) for enantioselective extraction processes are investigated. Structural results, such as the radial distribution function (RDF) and the combined distribution function (CDF), indicate that the hydroxyl hydrogen of menthol has a dominant interaction with the carbonyl oxygen of the acids in the considered DESs. The number of hydrogen bonds and non-bonded interaction energies formed between S-menthol and HBDs are larger than those with R-menthol, resulting in the self-diffusion coefficient of S-menthol being larger than that of R-menthol. Therefore, it can be said that the proposed DESs are good candidates for the separation of drugs with S chirality. The effects of acid type on the density and isothermal compressibility of DESs show the behaviour of DES2 > DES3 > DES1 and DES1 > DES3 > DES2, respectively. Our results provide a better perspective on new chiral DESs at the molecular level for enantioselective processes.