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In this paper, a series of equilibrium molecular dynamics simulations (EMD), steered molecular dynamics (SMD), and computational electrophysiology methods are carried out to explore water and ion permeation through mechanosensitive channels of large conductance (MscL). This research aims to identify the pore-lining side chains of the channel in different conformations of MscL homologs by analyzing the pore size. The distribution of permeating water dipole angles through the pore domains enclosed by VAL21 and GLU104 demonstrated that water molecules are oriented toward the charged oxygen headgroups of GLU104 from their hydrogen atoms to retain this interaction in a stabilized fashion. Although, this behavior was not perceived for VAL21. Numerical assessments of the secondary structure clarified that, during the ion permeation, in addition to the secondary structure alterations, the structure of Tb-MscL would also undergo significant conformational changes. It was elucidated that VAL21, GLU104, and water molecules accomplish a fundamental task in ion permeation. The mentioned residues hinder ion permeation so that the pulling SMD force is increased remarkably when the ions permeate through the domains enclosed by VAL21 and GLU102. The hydration level and potassium diffusivity in the hydrophobic gate of the transmembrane domain were promoted by applying the external electric field. Furthermore, the implementation of an external electric field altered the distribution pattern for potassium ions in the system while intensifying the accumulation of Cl

In this study, we introduce a superfast biomimetic water channel mimicking the hydrophobicity scales of the Aquaporin (AQP) pore lining. Molecular dynamics simulation is used to scrutinize the impact of hydrophilic doping level in the nanotube and the water-wall interaction strength on water permeability. In the designed biomimetic channel, the constructive interplay of Lennard-Jones (LJ) e parameters and hydrophilic doping levels increased the possibility of ultrafast water transport. Moreover, a unique set of LJ parameters is discovered for each biomimetic channel with different hydrophilic doping levels, enhancing water permeation. Inside high-performance biomimetic channels, water distribution surprisingly implies a varying pore geometry that narrows down in the middle, mimicking the pattern obtained from GplF pore analysis, evoking the narrow pore induced by the aromatic/arginine selectivity filter. This exciting accordance occurred as a result of tailoring specific hydrophilic arrays within the hydrophobic channel backbone by mimicking the AQP pore interior. The main takeaway of hydrophilic doping arrays implanted within the hydrophobic nanotube is to break the large barrier in the water-wall vdW energy profile into multiple reduced ones to increase water conduction. Consequently, the "water jumping" phenomenon in the middle of the biomimetic channel occurs under specific circumstances. The biomimetic channel with the highest value of water permeability of about 13.67 ± 0.66 × 10-13 cm3·s-1 exhibits the best mechanism for artificial water channels (AWCs), serving superfast water transport considering the low entrance barrier and weak water-wall interaction.

Microarrays play a determinant role in the detection and specification of biological molecules. The immobility of probe oligonucleotide with different sequences on the substrate surface is one of the main aims in designing of microarrays. In this regard, we select five different DNA single-strands to determine the best of probe single strand in the microarrays with a striped patterned double-layer graphene substrate. The results of the simulation illustrate that DNA single-strands on the substrate have distinct conformations related to each other. Thymine single strand has the maximum end to end distance and is more accessible for detecting target single strand in the microarrays. Also, the analysis of wettability results displays that the presence of a DNA single-strand in water drop decreases the amount of spreading of the droplets. Another important point is that the presence of a single strand increases the chance of water droplet pining on such surfaces.

A new solvent stimuli-responsive metallogel (VGel) was synthesized through the introduction of vanadium ions into an adenine (Ade) and 1,3,5-benzene tricarboxylic acid (BTC) organogel, and its supramolecular self-assembly was investigated from a computational viewpoint. A relationship between the synthesized VGel integrity and the self-assembly of its components is demonstrated by a broad range of molecular dynamics (MD) simulations, an aspect that has not yet been explored for such a complex metallogel in particular. MD simulations and Voronoi tessellation assessments, both in agreement with experimental data, confirm the gel formation. Based on excellent water stability and the ethanol/methanol stimuli-responsive feature of the VGel an easy-to-use visualization assay for the detection of counterfeit liquor with a 6% (v/v) methanol limit of detection in 40% (v/v) ethanol is reported. These observations provide a cheap and technically simple method and are a step towards the immersible screening of similar molecules in methanol-spiked beverages.

The current work investigates the separation of water–oil mixture on amorphous poly methyl methacrylate (PMMA) surface in the absence and presence of Anatase and Rutile titanium dioxide nanoparticles using molecular dynamics simulation. The presence of nano domains with positive and negative charges on PMMA surface causes the water molecules to form water clusters of various sizes. Water clusters can slide on the PMMA surface which leads to the formation of larger clusters and in continues formation of large clusters was the reason of separation water–oil mixture. In the presence of Anatase and Rutile nanoparticles, accumulation of water molecules around the particles leads to formation of larger water clusters and improves the separation of water–oil mixture. Anatase nanoparticle acts faster than Rutile nanoparticle in the adsorption of water molecules, while Rutile nanoparticle forms larger clusters and is more successful in adsorbing water molecules from the water–oil mixture. The orientation and the order parameter of water molecules in different layers from PMMA surface and around the Anatase and Rutile nanoparticles are investigated as well.

In this work, we investigate the effect of silicon substrate and temperature on the ice formation through molecular dynamics simulations. It was found that silicon substrate accelerates the ice formation rate. Depending on the temperatures of the systems, the formation rate can be accelerate or decelerated. The obtained results showed that, as the temperature increased from the lowest temperature 100K to the highest temperature 220K, the number of water molecules transformed into ice decreased. We found that the hydrophobic property of silicon is not a barrier for approaching ice formation. The high correlation between Si and the hydrogen atoms of water molecules stimulated the ice formation on the surface of silicon and allowed the formation of amorphous ice directly on the surface of silicon. The temperature effect on ice formation was in distinguishing two different behaviors one from 100K to 180K and the second above 180K. These behaviors were related to the temperature of which amorphous ice is stable. The results of the average number of hydrogen bonds and their lifetime are in parallel with the results of the number density profiles that can best explain how silicon affects the ice formation. The coordination number of water molecules increased with the decrease of the temperature for silicon substrate which means that bigger ice clusters were found. The ice molecules, which were formed near the silicon substrate, are more recognized than that of the bulk. To better understand these effects, bulk systems were used as comparative systems.

Increasing the hydrophobicity of polymeric surfaces, particularly polydimethylsiloxane (PDMS), has recently been the focus of research. In the present work, the wettability of smooth and rough PDMS surface was investigated. Surfaces with different chemical heterogeneity were examined for hydrophobicity using molecular dynamics simulation. In order to simulate surfaces with different heterogeneities, several distributions for the placement of polymer-forming atoms were taken into account. In addition, roughnesses with different distributions of the constituent atoms were applied to the polymer surfaces to increase hydrophobicity. As an indicator of the hydrophobicity, the contact angle was calculated using two approaches. Regarding the chemical heterogeneity of the polymeric surface, the simulation results showed that the contact angle and the radius of water droplets on the surface depended on the constituent atoms and their number, so that surfaces with more carbon atoms offered larger contact angles and smaller droplet radius, and thus more hydrophobicity. Furthermore, roughnesses rich in carbon also increased the surface hydrophobicity. It was concluded that the distribution of the constituent atoms of the polymeric surfaces played an essential role in water dispersion in that the number of carbon atoms at the pinning points of water droplets was higher than that of others.

Recently, graphene oxide has been widely used for the extraction of hydrocarbon compounds. In the present work, the separation of water from a water-oil mixture by two-layer graphene oxide has been studied using molecular dynamics simulation. Several interlayer spacing of graphene oxide layers was considered, and for each gap in each layer of graphene oxide, several sizes were considered and it was determined the efficient interlayer distance as well as gap size which gives highest water-oil separation. The simulation results unveil that as the interlayer spacing and the size of the gap is reduced, the flux and permeability of the water molecules decrease, but the amount of water molecules separating from the oil increases. To study the number of layers’ impact for higher separation efficiency, a system containing a graphene oxide layer was also studied and the importance of the number of graphene layers was highlighted. Also, for the analysis of graphene oxide functional groups’ effect on separation, a system containing graphene layers was also investigated and the role of functional groups was revealed in hydrogen bond formation between graphene oxide and water molecules. By calculating PMF, the effect of functional groups on the repelling oil molecules from the graphene oxide’s gaps was investigated.

In this work, desalination by multilayer graphene membranes with a rippled structure has been considered by molecular dynamics simulation. The (6, 7.5 and 9) A distances between the graphene sheets in a layer (gap wide) are selected. Also, these mentioned distances are applied as an interlayer space (channel height). Results of simulation demonstrate that multilayer graphene membranes with a rippled structure are more efficient in water flux than multilayer graphene membranes with an unrippled structure. These differences are more significant for membranes with 9 A interlayer space. In this work, it is shown that water flux in 9 A rippled membrane is 20% more than 9 A unrippled one. According to the simulation results, multilayer membranes with a rippled and unrippled structure are different significantly in the case of water flux, but they do not show many differences with each other in rejection. Also, it is shown that the effect of channel is more important than gap; because ions lose more number of water molecules when flow through the channel as compared to flow through gap or pores. From calculation of density, the water flux, ions rejection and coordination number of ions, the results of investigation are obtained.

Understanding the properties of the interface of water nano-droplet and rutile TiO2 (110) nanocrystal has attracted the attention of many surface scientists. In this research the interface of water nano-droplet and (110) plane of Rutile titanium dioxide nanocrystal along with the formation of water chains was studied based on a molecular dynamics approach. Density profiles of oxygen and hydrogen atoms of the water molecules show less movement in hydrogen atoms that reside closer to the TiO2 surface than the ones that are further away. The calculated results indicate that the average interlayer hydrogen bonds per water molecule is about 0.51 at the interface where water molecules form two different water-water hydrogen bonds with 28.55 and 670.24 ps lifetimes. The simulation data reveal the formation of one-dimensional chain structures of water on the TiO2 substrate. Certain values for the estimated angles among every three water molecules that participate in the formation of the chain structures is observed. The electrostatic energy contour map and the orientation of water molecules at the interface suggests that these molecules form ordered and periodic pair structures around the regions with high negative charge on titanium dioxide. The dynamical analysis of the water molecules indicates a dynamical independence from one another which results in their independent motion at the interface. Furthermore, the dynamical results also show that the water nano-droplet is pinned on the surface of titanium dioxide without any major movement.

Water adsorption and wetting of titanium dioxide surface along with its structure and dynamics of liquid water molecules has recently been studied as an important subject. In the current work, the interface of water and (110) surface of titanium dioxide is analyzed based on the formation and distribution of water molecules in the first and second layer from a molecular dynamics perspective. The simulation results illustrate that the water molecules form a linear chain in the interfacial layer, also known as the first layer. As the number of water molecules increases a second layer forms while the TiO 2 surface remains partially dry. Further increase results in the exchange of water molecules between first and second layers which facilitates the filling of the first layer. These results are extracted from density profiles, lifetime and number of hydrogen bonds in different layers, order parameter, mean squared displacement and, the orientation of water molecules at different distances from the surface all of which are in line with the reported quantum calculations and experimental data.

In this paper the adsorption behavior of a water droplet on the molybdenum disulfide and graphene surfaces were examined and compared. Results obtained from the calculation of the average of interaction energy between the water and the molybdenum disulfide surface and the graphene surfaces indicated that the van der Waals interaction plays an important role in the adsorption of water on these surfaces. The contour maps of the interaction energy between the water and the surfaces have revealed some different behaviors of the water droplet on these surfaces. The results showed that water sliding on the molybdenum disulfide surface and water pinning on the graphene surface is due to the difference in structural patterns of the surfaces. Molecular investigations of the water on the surfaces showed that the water molecules occupy continues positions on the molybdenum disulfide surface while they occupy discrete positions on the graphene surface. Two mechanisms for orientation and displacement of the water molecules on the surfaces were proposed. In addition, the effects of temperature and external field on movement of the water molecules on the surface were investigated. It was observed that the water - graphene system is more sensitive to the applied electric field than water-molybdenum disulfide system. In addition, the simulation results in the presence of the electric field showed that it is possible to take control of the water droplet on the graphite surface, so that the displacement of the water droplet can take place in a particular direction.

In this work, the melting/freezing point of confined water between two graphene sheets was calculated from the direct coexistence of the solid-liquid interface. Also, molecular dynamics simulation of confined liquid water-ice between two graphene sheets was applied. The phase transition temperature of the confined ice-water mixture was calculated as 240 K that was 29 K less than the non-confined ice-water system. In order to study the behavior of water molecules at different distances from the graphene sheets, 5 regions were provided using some imaginary planes, located between two graphene sheets. The obtained simulation results showed that water molecules located in the region near each graphene sheet with the thickness of 2 nm had a different behavior from other water molecules located in other regions. The results demonstrated that water molecules in the vicinity of graphene sheets had more mean square displacements than those in the middle regions.

In this study, adsorption of water nanodroplets, oil nanodroplets and oil–water mixtures on a poly vinylidene fluoride (PVDF) surface is investigated computationally by a molecular dynamics (MD) approach and a mechanism for adsorption of the droplets is proposed. MD simulation results revealed that the PVDF surface is hydrophobic and oleophilic and can be used to separate oil from water. The acquired results are in good agreement with experimental results. As to investigate the origins for hydrophobicity of the PVDF surface, mobility of water molecules on the PVDF surface has been meticulously investigated. Investigations have proven that once the water molecules are organized singly or in small groups with two or three molecules, they exhibit very low levels of mobility, whereas water molecules in groups of four or more have high mobility. Some descriptive studies were performed based on MD simulation results to investigate the behavior observed in the systems including: (i) distribution of partial charges on the surface of PVDF. (ii) Dependence of the orientation of water molecules near the PVDF surface on the size of water cluster. (iii) Dependence of the distance of water molecules to the PVDF surface on the water cluster size. Manner of charge distribution on the PVDF demonstrated a formation of nano-domains with positive and negative charges on the surface. Dependence of the behavior of water molecules on the nano-domains on the water cluster size was investigated.

This study provides a comprehensive investigation on the effect of epoxy crosslinking density and number of graphene layers on the interfacial mechanical behavior of graphene/epoxy nanocomposites. In particular, the graphene layers are detached in the normal and sliding directions within the framework of steered molecular dynamics, and the traction-separation curves are extracted for the whole separation process. The damage mechanism is also studied by analyzing the evolution of the local number density during pull-out tests. For better results interpretation, the variation of the interaction and adhesion energies, the number of pulled-out epoxy chains, and the distribution of crosslinked and uncrosslinked species are also investigated and discussed. Based on the results obtained, the crosslinking density has a significant effect on the interfacial properties between graphene and epoxy, especially in the normal mode. The damage behavior is also determined as the function of the epoxy crosslinking density so that at low crosslinking densities, the damage occurs in the polymer near the graphene, while the failure takes place in the interphase for higher crosslinking degrees. Increasing the number of graphene layers leads to a weaker interfacial strength, except for the double-layered graphene systems which have the highest traction peak among all samples.

Water and air pollutants have huge impacts on the entire living system. In addition, the newly emerging nanopollutants, increasing global warming, and consequent climate changes are posing major threats to the freshwater or fresh air availability. This has made it urgent to invent an appropriate water/air treatment technology that removes nanopollutants and also desalinates water to a significant extent. Carbon-based nanomaterials have generated marvelous interest in a wide range of research activities due to their high adsorption capacities. Carbon nanotubes, carbon nanotube bundles, and related materials have potential applications in gas/ion separation and water purification. Recently, gas/ion separation and water purification through carbon-based nanomaterials have received increasing attention. This review summarizes the properties of carbon nanotubes and carbon nanotube bundles related to gas separation, ion separation, and water purification using molecular dynamics simulations. Membranes-based carbon nanomaterials show promise of water purification and gas separation. These attractive properties of carbon nanotubes-based and carbon nanotube bundles-based nanomaterials make them proper candidates for gas separation, gas molecular-sieving processes, and desalination purposes in nanoscale dimensions.

We present an investigation on the permeability and selectivity of graphene sheets with designed sub nanometer pores using molecular dynamics simulations. We show that nanoporous graphene can be used to separate water from a gaseous mixture of nitrogen, oxygen and water. The obtained results show that the separation is performed based on the absorption of water molecules on the nanoporous graphene surface. Pore size plays an important role in the possible formation of water clusters on the nanoporous graphene surface. In graphene sheets with large pores, the space between the neighboring graphene becomes smaller and water molecules form a cluster on the graphene surface quickly. Because the size of the water clusters is larger than that of the nanopore, they cannot pass through it, whereas nitrogen and oxygen molecules are able to pass through the nanoporous graphene. In this study, we propose a mechanism for the formation of water clusters on the nanoporous graphene surface. To illustrate the different steps of the proposed mechanism, several investigations were performed such as calculation of the distribution and accumulation of water molecules on the graphene surface, angle between the dipolar moment vector of water molecules and the graphene surface and formation and movement of multi-layer clusters. Moreover, a specific method to pass N2 and O2 molecules through nanoporous graphene is presented.

In this work, we compared the structural and dynamical properties of water confined between two graphene oxide (GO) sheets with water confined between two graphene sheets through molecular dynamics simulations. Our results showed how the structure and dynamics of the water near the GO surfaces changes under confinement conditions. Different orientations of the water molecules to the GO sheets confirm the heterogeneous nature of the confined water. The density distribution of water near the GO sheets is different from the graphene surfaces due to the presence of hydrophilic functional groups of the GO sheets. Also, the hydrogen bonds between the water molecules are disturbed due to the presence of these groups on the GO surfaces. The results showed that as water molecules in areas which are close to the GO surfaces are isolated, and due to hydrogen bond formation between water molecules and the substituents of the GO, the water molecules have fewer hydrogen bonds with other water molecules around. In the middle region between two GO sheets, it has been seen that each water molecule is surrounded by more water molecules, and there are many more hydrogen bonds, so it is possible to consider a network structure of water in this region. There is a good quantitative agreement between experiments and the above mentioned results. These results were confirmed by the calculated coordination number, radial distribution functions and mean square displacements.

In this work, the liquid–solid phase transition temperature of water confined between two graphene oxide (GO) sheets is investigated using molecular dynamics simulations. The results demonstrate that, due to the presence of functional groups of the GO sheets, at temperatures below liquid–solid phase transition temperature, the water molecules near the confining sheets are not structured like ice and remained in the liquid form. The results also reveal the confinement effects on the melting and freezing rate of water molecules. The confining conditions delay the freezing process of the water molecules compared to the bulk water molecules. These results are confirmed by the calculated total energy, the density profile of water molecules confined between two GO sheets, the number of hydrogen bonding, radial distribution function, and mean square displacement. The liquid–solid phase transition temperature of water in the presence of GO sheets was calculated as 236 K, which was 34 K less than the temperature of the bulk water.

Having performed simulations for the pure water and water–NaCl salt mixture at several temperatures, we reveal new aspects of the formation of unstable clathrate-like water molecules in coexistence with ice molecules. Interestingly, the maximum numbers of water molecules in clathrate hydrate phase are recorded at freezing/melting points of the pure water and water–salt mixture. In the presence of NaCl salt, the number of water molecules in the unstable formed clathrate phase decreases. We first perform molecular dynamics simulations using the coarse-grain model to study the freezing/melting behavior of the pure water and 14% water–salt mixture at several temperatures. For both systems, the freezing/melting behavior of water molecules is studied using some qualities such as density, number of ice molecules, coordination number, and liquid fraction. From the results of our study, we also show that calculating the coordination numbers of water, sodium and chloride ions at different temperatures can serve as a useful method for determining the freezing/melting temperature for the pure water and salty water, and also for the brine rejection process for water–salt mixture. In the pure water, large changes occur at the freezing/melting point for the coordination numbers both for the first and higher coordination shells.

In this work, we have performed molecular dynamics (MD) simulations to investigate the effects of confinement in a (20,20) single-wall carbon nanotube (SWCNT) on the behavior of a mixture of water and 1-n-propyl-4-amino-1,2,4-triazolium bromide ([part][Br]) ionic liquid (IL). The effects of water mole fraction were examined on the structural and dynamical properties of water/IL mixture and confined water/IL mixture. The total energy, the interaction energy between molecules and the radial distribution functions (RDFs) were calculated and compared at different water mole fractions for both water/IL mixture and confined water/IL mixture. The obtained results show that for the confined water/IL mixtures, the most interaction energy value is observed in pure water and pure IL systems. The analysis of the RDFs between different atoms of IL, water and SWCNT shows that the presence of SWCNT leads to a stronger spatial correlation between the water and IL molecules. Also, investigating the dihedral angle between the surface of SWCNT and the cation ring plane shows that the cations tend to orient their rings mainly parallel to the SWCNT surface. Finally, we calculated and compared the dynamics of the water molecules, anions, and cations at different water mole fractions in water/IL mixture and confined water/IL mixture. Two different regimes were observed for the confined and the bulk mixtures in low and high water mole fractions.

Using molecular dynamics (MDs) simulations, the adsorption of a nitrogen–oxygen mixture (representing air) on (8, 8), (10, 10), and (12, 12) single-walled carbon nanotube (SWCNT) bundles is investigated as a function of temperature, air loading and diameter of nanotubes at subcritical ( T = 100 K) and supercritical ( T = 200 and 300 K) temperatures of the air. In order to do this, heat of adsorption, diffusion coefficients, activation energy, and radial distribution functions (RDFs) were computed for further analysis of the adsorption process. The simulation of exposing air on nanotube bundles, show that the amount of adsorption, heat of adsorption, and diffusion coefficients are strongly influenced by the applied temperature, i.e., along with the temperature increase, the amount of adsorption would be reduced. Furthermore, the results show that oxygen is selectively adsorbed relative to nitrogen, so carbon nanotubes (CNTs) can be considered as promising gas-filtering systems in addition to their previous gas-storage capability.

Molecular dynamics (MD) simulations were performed to investigate the interfacial binding between the single-walled carbon nanotubes (SWCNTs) and conjugated polymers including polythiophene (PT), polypyrrole (PP), poly(2,6-pyridinylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene) (PPyPV), and poly(m-phenylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene) (PmPV). The intermolecular interaction energy between SWCNTs and polymer molecules was computed, and the morphology of polymers physisorbed to the surface of nanotubes was investigated by the radius of gyration (R(g)) and the alignment angle (theta). The influence of nanotube radius and temperature on the interfacial adhesion of nanotube-polymer and R(g) of polymers was explored more. Our simulation results showed that the strongest interaction between the SWCNTs and these conjugated polymers was observed, first for PT, then PPy and PmPV, and finally PPyPV. Furthermore, we compared our results to the work by Yang and his co-workers (J. Phys. Chem. B 2005, 109, 10009). Our results show that the intermolecular interaction in our systems is strongly influenced by the specific monomer structure of polymer and nanotube radius, but the influence of temperature could be negligible. The high values of intermolecular interaction energy of such composites suggest to us that an efficient load transfer will exist in the interface between nanotube and heterocyclic conjugated polymer, which is of a key role in the composite reinforcement practical applications.

Quaternary (liquid + liquid) equilibrium (LLE) data of the aqueous two-phase poly (ethylene glycol), poly (N,N-dimethylacrylamide-t-butylacrylamide) with abbreviation name poly (DMAM–TBAM) as a hydrophobic association water-soluble copolymer and KH2PO4 has been determined experimentally at T = 338.15 K. Furthermore, the generalized Flory–Huggins theory with two electrostatic terms (the Debye–Huckel and Pitzer–Debye–Huckel) was used for correlation of the phase behavior of the quaternary system and the interaction parameters between all species were calculated. It was found that addition of poly (DMAM–TBAM) copolymer as well as changing the temperature can shift the binodal curves of aqueous two-phase systems containing polyethylene glycol (PEG) and salt. Also, the phase behavior of the DMAM–TBAM copolymer with some salts containing sodium chloride, ammonium hydrogen phosphate, potassium hydrogen phosphate, and sodium carbonate were studied experimentally at T = 338.15 K and the effect of the salt type on the their binodal curves was determined.

(Liquid + liquid) equilibrium (LLE) data of quaternary aqueous system containing polyoxyethylene (20) cetyl ether (with abbreviation name Brij 58, non-ionic surfactant), diammonium hydrogen phosphate, and poly ethylene glycol (PEG) with three molar masses { M W = (1000, 6000, and 35,000) g · mol −1 } have been determined experimentally at T = 313.15 K. Furthermore, the Flory–Huggins theory with two electrostatic terms (Debye–Huckel and Pitzer–Debye–Huckel equations) have been used to calculate the phase behavior of the quaternary systems and (surfactant + polymer) interaction parameter as well as interaction parameters between other species. Temperature dependency of the parameters of the Flory–Huggins theory has been obtained. Also an effort have been done to show that addition of PEG as well as increasing the temperature can shift the binodal curves of the ternary aqueous system containing surfactant and salt to lower mole fraction of salt. Also the effect of polymer molar mass on the binodal diagram displacement has been discussed.

The effect of temperature on the (liquid + liquid) equilibrium of the aqueous solution of surfactant polyoxyethylene cetylether (with abbreviation name Brij 58) and diammonium hydrogen phosphate has been investigated at T = (303.15, 313.15, 323.15, and 333.15) K. The Flory–Huggins equation with two electrostatic terms (Debye–Huckle and Pitzer–Debye–Huckle equations) was used to correlate the phase behavior of this system. Good agreement has been found between experimental and calculated data from both models. The results indicated that the enlargement of the two-phase region upon increasing the temperature. Additionally temperature dependency of the parameters of the Flory–Huggins model has been calculated.

A quaternary (liquid + liquid) equilibrium study was performed to focus attention on the interaction parameters between poly-N-vinylcaprolactam (PVCL) and poly-ethylene glycol (PEG) as well as between other species. At first, the new experimental data of (liquid + liquid) equilibria for aqueous two-phase systems containing PEG, KH2PO4, and PVCL at T = 303.15 K have been determined. Then the Flory–Huggins theory with two electrostatic terms (the Debye–Huckel and the Pitzer–Debye–Huckel equations) has been generalized to correlate the phase behavior of the quaternary system. Good agreement has been found between experimental and calculated data from both models especially from the Pitzer–Debye–Huckel equation. Also an effort was done to compare the effect of temperature as well as addition of PVCL on the binodal curves of PEG, KH2PO4, and water. The effect of the type of salt on the binodals has been also studied, and the salting out power of the salts has been determined.

The Flory–Huggins model with two electrostatic terms (the Debye–Huckel and Pitzer–Debye–Huckel equations) and the Osmotic virial model were used to correlate the liquid–liquid equilibrium data of the aqueous solution of polyvinylpyrrolidone and diammonium hydrogen phosphate/ammonium dihydrogen phosphate buffer at various temperatures (298.15, 308.15 and 318.15 K) and pH 5 and 7. The obtained interaction parameters of models were used to calculate the activities of water, polymer and salt at three temperatures and both pH values. The deviations showed that these models can accurately correlate the activities of all species.

In the present work the Flory–Huggins model with two electrostatic terms (the Debye–Huckel equation and Pitzer–Debye–Huckel equation) and the osmotic virial model have been used to obtain the activities of polymer, salt and water for the liquid–liquid equilibrium of the aqueous polyvinylpyrrolidone + potassium dihydrogen phosphate/dipotassium hydrogen phosphate buffer at various temperatures (298.15, 308.15 and 318.15 K) and pH 5 and 7. The effects of the temperature and pH on the activities of polymer, salt and water have been investigated. To investigate the predictive performance of these models, the energetic interaction parameters were estimated by minimizing the proper objective function using the singular value decomposition method. The very low deviations obtained suggested that the models studied provide a very good predictive description of the system investigated.

This work was aimed to investigate the behavior, morphology, structure, and dynamical properties of pure ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) confined between two parallel and flat graphene sheets at different interwall distances, H. Thus, molecular dynamic (MD) simulations were performed for different interwall distances including (10, 14, 16, 20, 23, and 28) A at seven temperatures from 278 to 308 K. These results showed that the distribution and orientation of cations and anions on the graphene sheets depended on H. At the shortest H, a dense monolayer of the anions and cations was formed between two graphene sheets. The number of these layers increased as H increased. The potential energy diagram as a function of H demonstrated a minimum potential energy at H = 16 A. Also, there was a minimum overlap between the density profiles of the cations and anions at H = 16 A. Diffusion coefficients of the cations and anions increased as temperature and H increased. Moreover, slope of the plot of the diffusion coefficients of the cations and anions versus H significantly changed at H = 16 A. Orientation functions revealed that most of the cations oriented parallel to the graphene sheets.

In this work, we used a molecular dynamics (MD) simulation approach to investigate the interfacial binding of boron nitride nanotubes (BNNTs) with poly[m-phenylenevinylene-co-(2,5-dioctyloxy-p-phenylenevinylene)] (PmPV), polystyrene (PS), and polythiophene (PT). Quantum partial charges of BNNT-polymer composites were determined by density functional theory (DFT) calculations and then included in MD simulations. The interaction energy between nanotubes and polymer molecules was computed, and the morphology of polymers stacked onto the surface of the nanotubes was investigated based on the dihedral angle (θ). Our results confirm that the interaction energy is strongly influenced by the specific monomer structure of polymer and nanotube radius, but the influence of temperature is likely negligible. Among the investigated polymers, PT possesses the strongest adhesion to the BNNTs, followed by PmPV and PS. Moreover, the comparison of our results for BNNT-polymer composities with those of the similar carbon nanotube (CNT)-polymer composites reveals that the BNNT-polymer interactions are much stronger, which is the most important result of this work. This finding is also in good agreement with recent experimental observations. The higher values of interaction energy of BNNT-polymer composites suggest that the BNNTs could be more efficient nanofillers than the CNTs for nanocomposite reinforcement applications.

Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multifunctional characteristics due to their unique physiochemical properties and prospective applications in various nanotechnologies. However, current techniques of CNTs fabrication cannot produce homogenous CNTs, and this prevents the widespread use of CNTs. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. Techniques for separating bundles of CNTs into homogeneous dispersion are still under development. The preparation of effective dispersions of CNTs presents a major impediment to the extension and utilization of CNTs. CNTs intrinsically tend to bundle and/or aggregate. The prevention of such behavior has been explored by testing various techniques to improve the dispersibility of CNTs in a variety of solvents. There are mainly two approaches to obtain a good quality dispersion; chemical functionalization and physical interactions. The chemical functionalization technique has been found effective, but deteriorates the intrinsic properties of CNTs through the introduction of defects in the wall. Physical blending approaches with the ultrasound and high speed shearing have been proven capable of debundling CNTs and stabilizing individual CNTs while maintaining their integrity and intrinsic properties. Contemporary methods for dispersion of CNTs in aqueous media are discussed and most attention is paid to molecular dynamics simulation techniques and other physical techniques, as well as to the use of various surfactants and polymers.

Ionic liquids (ILs) with interesting and useful properties are usually organic salts which have an asymmetric organic cation and a wide assortment of anions. Mixing ILs and some materials like nano structures adjusts their properties positively. This paper reviews the recent computational molecular dynamics studies about mixture of ILs and some materials including carbon nanotubes (CNT), gases and water. Below we mention some reported results in this review. In the case of ILs–CNT systems, we review the behavior of ILs in the CNT dispersing. The results show that ILs cannot disperse the bundled single-walled CNTs, but it can disperse some aggregated non-bundled ones. In the case of confined water/IL mixtures, the obtained results show that the most interaction energy value is observed in pure water and pure IL systems. It was shown in the case of absorption of gases such as SO2 by ILs systems, that the diffusion coefficient of cation in the pure ILs and IL/SO2 gas mixtures was greater than that of the anions and much less than that of the SO2 molecules. In addition, in comparison with pure ILs, the presence of SO2 leads to an increase in the diffusion coefficients, conductivity, density and heat capacity of the ionic species of the IL/SO2 gas mixtures.