Size Of Solvent Molecules Research Articles

Tailored porous structure and CO2 adsorption capacity of Mg-MOF-74 via solvent polarity regulation

Metal-organic frameworks (MOFs) are promising materials for CO2 adsorption and capture. The unique crystal structure and the open porous structure of MOFs are key factors affecting their CO2 adsorption performance, but the precise tuning of MOF structures remains a challenge. Herein, we applied the Kamlet-Taft method to investigate the effect of solvent proton-supplying/accepting capaity (β/α parameters) on the structure and CO2 adsorption performance of Mg-MOF-74 by tuning the reaction solvent polarity. It was found that the ratio of the nucleation rate/growth rate of Mg-MOF-74 could be effectively controlled by adjusting the β/α value of the solvent, realizing the regulation of the crystal structure and morphology of Mg-MOF-74. In addition, the size of solvent molecules played a crucial role in the pore size of Mg-MOF-74. Interestingly, the solvent molecules were competitively coordinated with ligands and participate in the growth of Mg-MOF-74 upon decreasing the β/α value. The crystal structure, morphology and pore size of Mg-MOF-74 could be precisely regulated by the β/α value and molecular size of the reaction solvent, and the highest performing Mg-MOF-74 exhibited a CO2 adsorption capacity of 7.38 mmol/g.

An Uncommon Solvent‐Controlled Photochromic Tetraphenylethylene‐Based Co‐crystal

AbstractA co‐crystal FJU‐182 with a closed cage structure with photochromic phenomenon was formed using a tetraphenylene derivatives 4,4′,4′′,4′′′‐(anthracene‐9,10‐diylidenebis(methanediyl‐ylidene))tetrabenzoic acid self‐assembled with 1,3‐di(4‐pyridyl)propane in a solvent. It was also found that isomorphic crystals grown from different solvents exhibited different fluorescence. The electron paramagnetic resonance and X‐ray photoelectron spectroscopy data showed that the photochromic mechanism of crystal FJU‐182 was due to photoinduced electron transfer, while the different color change of crystals grown from different solvents was attributed to the size of solvent molecules. The I−V curves of the crystals FJU‐182 before and after illumination were also tested, and it was found that the conductivity of the crystals before the color change would be 3–8 times higher than the conductivity of the crystals after the color development. FJU‐182 provides a new case for electrochemical devices with photoelectric response.

First-Principles Modeling of Preferential Solvation in Mixed-Modifier Differential Mobility Spectrometry.

Differential mobility spectrometry (DMS) separates ions based on mobility differences between high and low electric field conditions. To enhance resolution, solvents such as water and acetonitrile are often used to modify the collision environment and take advantage of differing dynamic clustering behavior between analytes that coelute in hard-sphere environments (e.g., N2). When binary solvent mixtures are used to modify the DMS environment, one solvent can have a dominant influence over the other with respect to ion trajectories. For example, for quinoline derivatives, a 9:1 water:acetonitrile solvent mixture exhibited identical behavior to an environment containing only acetonitrile as a modifier. It was hypothesized that this effect arises due to the significantly different binding strengths of the two solvents. Here, we utilize a first-principles model of DMS to study analytes in single and binary solvent mixtures and explore the effects governing the dominance of one solvent over the other. Computed DMS dispersion curves of quinoline derivatives are in excellent agreement with those measured experimentally. For mixed-modifier environments, the predicted cluster populations show a clear preferential solvation of ions with the stronger binding solvent. The influence of ion-solvent binding energies, solvent concentration, and solvent molecule size is discussed in the context of the observed DMS behavior. This work can guide the usage of binary solvent mixtures for improving ion separations in cases where compounds coelute in pure N2 and in single-solvent modifier environments. Moreover, our results indicate that binary solvent mixtures can be used to create a relative scale for solvent binding energies.

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.

Size Effects in Sodium Ion Batteries

AbstractSodium ion batteries (SIBs) are promising candidates for large‐scale energy storage owing to the abundant sodium resources and low cost. The larger Na+ radius (compared to Li+) usually leads to sluggish reaction kinetics and huge volume expansion. One of the efficient strategies is to reduce the size of electrode materials or the components of electrolytes to a suitable scale where size effect begin to emerge, leading to the improved or varied thermodynamics, kinetics, and mechanisms of sodium storage. However, only a few systematic reviews address size effects in SIBs, which requires further attention urgently. Herein, after a brief discussion of the general size effect, the size‐related kinetics, thermodynamics (equilibrium voltage and morphology), and sodium storage mechanisms (phase transition, conversion reaction, interfacial, and nanopore storage) of electrode materials are presented. The size effect on liquid, polymer, and inorganic solid‐state electrolytes are discussed as well, including the size of solvent molecules, Na salts, and inorganic fillers. Finally, neutral and adverse size effects are discussed, and some useful strategies are proposed to overcome them. The deep insights into the size effect will provide instructive guidelines for developing SIBs and other new energy storage systems.

Molecular dynamics simulations of solvent evaporation-induced repolymerization of covalent adaptable networks

Covalent adaptable networks (CANs) can be decomposed in suitable solvents via bond exchange reactions. Repolymerization can occur by heating the decomposed solution and evaporating the solvent. This solvent-assisted decomposition and repolymerization approach can be used to recycle CANs. In this study, the solvent evaporation from decomposed CAN solutions along with the repolymerization of decomposed chain segments are investigated using molecular dynamics simulations. The evolution of density profiles and chain segment lengths are presented to characterize the solvent evaporation and network repolymerization. The effects of solvent molecule size and evaporation rate on the evaporation and repolymerization processes are analyzed. Our results show that a polymer-rich layer at the solution surface quickly forms when evaporating into a vacuum. The polymer-rich layer significantly inhibits the evaporation of solvent molecules with larger size. Molecules have sufficient time to diffuse when evaporating at a slow rate, thus a more homogenous density distribution can be achieved.

Ion Dynamics of Water‐in‐Salt Electrolyte with Organic Solvents in Nanoporous Supercapacitor Electrodes

AbstractWater‐in‐salt electrolytes blended with organics solvents, that is, organic solvent/water mixed electrolytes, are promising for applications in next‐generation energy storage devices vitally needed for industrial electrification and decarbonization. However, the electrolyte ion diffusion behaviors within nanoporous supercapacitor electrodes are poorly understood. Here a systematic investigation into supercapacitor resistances and ion kinetics is carried out experimentally and with numerical simulations. The electrochemical results on the nanoporous electrodes reveal a nonmonotonic (decreasing, increasing, and then decreasing) trend of supercapacitor resistances with increasing solvent mobility, challenging the long‐held views that supercapacitor resistances decrease with elevated mobility of organic solvent. The abnormal trend is examined by numerical molecular dynamics simulations of electrolyte ion diffusion within 0.95 nm nanochannels. The electrolyte conductivity is related to cation–anion interactions within nanochannels. We further confirm the crucial interplay of the van der Waals sizes of solvent molecules and channel width in determining electrolyte conductivity in nanoporous electrodes.

A molecular dynamics study of decomposition of covalent adaptable networks in organic solvent

It has been recently reported that covalent adaptable networks can be decomposed in organic solvents. This prominent feature provides exciting opportunities to recycle thermosets and their composites. In this paper, a molecular dynamics computational framework is established to investigate the decomposition of an epoxy covalent adaptable network in ethylene glycol solvent via transesterification-type bond exchange reactions. The simulations describe the interdiffusion between polymer and solvent. Additionally, the degradation of polymer network is investigated by calculating the monomer number of each polymer chain and analyzing the evolution of ester conversion. Finally, the covalent adaptable network decomposition in octamethylene glycol is simulated to study the influence of solvent molecule size. This work is the first one to use the molecular dynamics to study the decomposition of covalent adaptable network. The simulation results advance the understandings of the decomposition kinetics and provide a guideline for the selection of suitable solvents.

The Phase Transformation and Formation Mechanism of Isostructural Solvates: A Case Study of Azoxystrobin

Azoxystrobin has one amorphous form and two solvent-free forms. A series of new solvates were obtained by crystallization experiments in 40 solvents. Among these solvates, four of them were successfully determined by single-crystal X-ray diffraction and analyzed in terms of molecular conformation, intermolecular interaction, and crystal-packing motifs. In addition, the physiochemical properties of all solvates were further studied and presented with comprehensive characterization. It was found that both properties and the size of solvent molecules attribute to the formation of isostructural azoxystrobin solvates. Isostructural solvates can be formed when the solvents have particular molecular size (molar volume ranging from 56.1 to 88.5 cm3/ mol) and solvent properties that could make weak interactions with azoxystrobin. Desolvation and formation mechanism of isostructural solvates were investigated through the phase transformations and crystal structure analysis. The desolvation of solvates first forms f...

Dynamic Behaviors of Solvent Molecules Restricted in Poly (Acryl Amide) Gels Analyzed by Dielectric and Diffusion NMR Spectroscopy.

Dynamics of solvent molecules restricted in poly (acryl amide) gels immersed in solvent mixtures of acetone–, 1,4-dioxane–, and dimethyl sulfoxide–water were analyzed by the time domain reflectometry method of dielectric spectroscopy and the pulse field gradient method of nuclear magnetic resonance. Restrictions of dynamic behaviors of solvent molecules were evaluated from relaxation parameters such as the relaxation time, its distribution parameter, and the relaxation strength obtained by dielectric measurements, and similar behaviors with polymer concentration dependences for the solutions were obtained except for the high polymer concentration in collapsed gels. Scaling analyses for the relaxation time and diffusion coefficient respectively normalized by those for bulk solvent suggested that the scaling exponent determined from the scaling variable defined as a ratio of the size of solvent molecule to mesh size of polymer networks were three and unity, respectively, except for collapsed gels. The difference in these components reflects characteristic molecular interactions in the rotational and translational diffusions, and offered a physical picture of the restriction of solvent dynamics. A universal treatment of slow dynamics due to the restriction from polymer chains suggests a new methodology of characterization of water structures.

Effects of solvent and wall roughness on the dynamics and structure of a single polymer in a slit

The structure and dynamics of polymers in confinements (such as porous media, channels and slits) depend not only on the characteristic length scales of the confinements but also on solvent types and interactions between polymers and confinement constituents. In this study, we show by performing both molecular dynamics (MD) and Langevin dynamics (LD) simulations that the lateral diffusion of a single flexible polymer in a good solvent in a slit should be determined by a complicated interplay among the slit height (H), solvent types and slit wall roughness. The slit wall roughness is tuned by employing either corrugated walls or smooth walls. We find from simulations that only when solvent molecules are implemented explicitly in MD simulations, the wall roughness makes a qualitative difference in the lateral diffusion coefficient (D∥) of the polymer: as H is decreased, D∥ increases for smooth walls while D∥ decreases for corrugated walls. Such a qualitative difference in D∥ should be a solvent-mediated effect, which is not observed for implicit solvent models in LD simulations. The single polymer in the slit with the explicit solvent model follows Zimm dynamics while the polymer follows Rouse dynamics with the implicit solvent models. In the meantime, the wall roughness hardly affects the structure of the polymer in the slit. The density distribution functions of monomers (ρm(z)) and solvent molecules (ρs(z)) do not depend on whether the walls are corrugated or smooth. The radius of gyration (Rg) is also insensitive to the wall roughness. On the other hand, the solvent model gives rise to a qualitative difference in ρm(z) and Rg, especially when the height (H) of the slit is small. For sufficiently small values of H, ρm(z) depends on the size of solvent molecules used in the explicit solvent model. However, regardless of the solvent model and wall roughness, the scaling exponent (ν) of Rg and the degree of polymerization (N) (i.e., Rg∼Nν) changes gradually from 0.6 to 0.75 as H decreases.

Solvates of Dasatinib: Diversity and Isostructurality

A series of dasatinib crystalline forms were obtained, and a hierarchical cluster analysis of their powder X-ray diffraction patterns was performed. The resulting dendrogram implies 3 structural groups. The crystal structures of several solvates representing 2 of these groups were determined. The crystal structure analysis confirms the isostructurality of solvates within structural group I and suggests a correlation between solvent molecule size and trends in crystal structures within this group. In addition, the formation relationships in 2-solvent media between different dasatinib solvate groups were determined. The formation preference of solvates was found to follow the ranking group I > group III > group II.

Effect of the size of solvent molecules on the single-chain mechanics of poly(ethylene glycol): implications on a novel design of a molecular motor.

Excluded-volume (EV) interaction, also known as the EV effect, can drive the collapse of polymer chains in a polymer solution and promote the crystallization of polymer chains. Herein we report, for the first time, the effect of EV interaction on the single-chain mechanics of a polymer, poly(ethylene glycol) (PEG). By using AFM-based single-molecule force spectroscopy, the single-chain mechanics of a PEG chain has been detected in various nonpolar organic solvents with different molecule sizes. It is observed that the nonpolar solvents can be classified into two categories. In the small-sized organic solvents (e.g., tetrachloroethane and n-nonane), PEG presents its inherent elasticity, which is consistent with the theoretical single-chain elasticity from quantum mechanical calculations. However, in the middle-sized solvents (e.g., n-dodecane and n-hexadecane), the single-chain entropic elasticity of PEG is influenced by EV interactions noticeably, which indicates that the PEG chain tends to adopt a compact conformation under these conditions. To stretch a PEG chain from a free state to a fully extended state, more energy (1.54 kBT per repeating unit) is needed in small-sized organic solvents than in middle-sized organic solvents. It is expected that a partially stretched PEG chain would shrink to some extent when the solvent is changed from a middle-sized organic solvent to a small-sized one. Accordingly, a novel design of a PEG-based single-molecule motor that works with solvent stimuli is proposed.

Nanoconfined catalytic Ångström-size motors.

Self-propelled chemically powered synthetic micron and nano-scale motors are being intensively studied because of the wide range of potential applications that exploit their directed motion. This paper considers even smaller Ångström-size synthetic motors. Such very small motors in bulk solution display effects arising from their self-propulsion. Recent experiments have shown that small-molecule catalysts and single enzyme molecules exhibit properties that have been attributed to their chemical activity. Molecular dynamics is used to investigate the properties of very small Ångström-size synthetic chemically powered sphere-dimer motors in a simple atomic-like solvent confined between walls separated by distances of tens of nanometers. Evidence for strong structural ordering of the motors between the walls, which reflects the finite size of solvent molecules and depends on solvent depletion forces, is provided. Dynamical properties, such as average motor velocity, orientational relaxation, and mean square displacement, are anisotropic and depend on the distance from the walls. This research provides information needed for potential applications that use molecular-scale motors in the complex confined geometries encountered in biology and the laboratory.

Pressure-induced conformation transition of o-phenylene solvated in bulk hydrocarbons.

The conformational behavior of o-phenylene 8-mers and 10-mers solvated in a series of linear alkane solvents by means of classical molecular dynamics and first-principles calculations was studied. Irrespective of the solvent used, we find that at ambient pressure the molecule sits in the well-defined close-helical arrangement previously observed in light polar solvents. However, for pressures greater than 50 atm, and for tetradecane or larger solvent molecules, our simulations predict that o-phenylene undergoes a conformational transition to an uncoiled, extended geometry with a 35% longer head-to-tail distance and a much larger overlap between its lateral aromatic ring groups. The free energy barrier for the transition was studied as a function of pressure and temperature for both solute molecules in butane and hexadecane. Gas-phase density functional theory-based nudged elastic band calculations on 8-mer and 10-mer o-phenylene were used to estimate how the pressure-induced transition energy barrier changes with solute length. Our results indicate that a sufficiently large solvent molecule size is the key factor enabling a configuration transition upon pressure changes and that longer solute molecules associate with higher conformation transition energy barriers. This suggests the possibility of designing systems in which a solute molecule can be selectively "activated" by a controlled conformation transition achieved at a predefined set of pressure and temperature conditions.

Series of solvent-induced single-crystal to single-crystal transformations with different sizes of solvent molecules.

A highly stable soft porous coordination polymer (PCP), namely [Cu3(TP)4(N3)2(DMF)2]·2H2O·2DMF (1), has been synthesized via an in situ synthesis of 4-tetrazole pyridine (TP) under solvothermal conditions (DMF = N,N'-dimethylformamide). Remarkably, the solvent molecules in 1 can be respectively exchanged with cyclohexane (C6H12), cyclopentane (C5H10), decahydronaphthalene (C10H18), 1,4-dioxane (C4H8O2), and tetrahydropyrane (C5H10O) in single-crystal to single-crystal (SCSC) manners to yield [Cu3(TP)4(N3)2(DMF)2]·3C6H12 (1a), [Cu3(TP)4(N3)2(DMF)2]·2C5H10 (1b), [Cu3(TP)4(N3)2(DMF)2]·H2O·C10H18 (1c), [Cu3(TP)4(N3)2(DMF)2]·C4H8O2 (1d), [Cu3(TP)4(N3)2]·3C4H8O2 (1e), and [Cu3(TP)4(N3)2]·2H2O·C5H10O (1f). Further, the occluded cyclohexane molecules in 1a can be removed by heating to give its porous guest-free form [Cu3(TP)4(N3)2(DMF)2] (1g). Particularly, in water, 1 can lose its coordinated N3(-) anions to generate [Cu(TP)2(H2O)4]·4H2O (1h). More interestingly, the soft PCP (1) demonstrates the guest selectivity for the cycloalkane solvents, namely cyclohexane, cyclopentane, and decahydronaphthalene, in SCSC manners for the first time, attributed to the synergy effect between the size and geometry of the solvent and the shape of the framework cavity. Moreover, the desolvated samples of 1e show the highly selective gas adsorption of CO2 over N2, indicating its potential application in the separation of the CO2/N2 mixture.

Performance of thermally-chargeable supercapacitors in different solvents.

The influence of solvent on the temperature sensitivity of the electrode potential of thermally-chargeable supercapacitors (TCSs) is investigated. For large electrodes, the output voltage is positively correlated with the dielectric constant of solvent. When nanoporous carbon electrodes are used, different characteristics of system performance are observed, suggesting that possible size effects must be taken into consideration when the solvent molecules and solvated ions are confined in a nanoenvironment.

Transfer processesin polymermembranes. Part 3

The basic thermodynamic parameters and conditions of dissolution of organic liquid in polymers are considered in the paper. Today, the problem of predicting the solubility of organic substances of multicomponent mixtures in polymeric membranes is highly relevant in the selection of polymeric materials to create pervaporation membranes. Clear and unambiguous explanations for the dissolution process, and relationship between the basic thermodynamic parameters of spontaneous dissolution or mixing are given in the paper. It is shown that at spontaneous dissolution and , the more the absolute value of these values is, the further the system is from the equilibrium state, the greater the affinity of the system components is and the higher the solubility degree is. Besides, the solubility will take place at any ratio of components, if the molar enthalpy of mixing ∆H mix is close to zero, i.e. when ∆H mix → 0 and , and then the polymer can be dissolved in the given solvent. It is experimentally proved that some solvents can be adsorbed in the active layer of the polymer, but not penetrate into the zone of dissolution phase, although according to the values of HSP parameters, they should be well dissolved. Such deviations may be connected with the sizes of solvent molecules.

Influence of size of solvent molecules on structural and thermodynamic properties of the electrode/electrolyte interface

The influence of size of solvent molecules on the structural and thermodynamic properties of the interface between the electrode and electrolyte, using the solvent primitive model, was studied by grand canonical Monte Carlo (GCMC) simulations. The computer simulation results are compared with those obtained from the modified Poisson–Boltzmann (MPB) theory. The ionic singlet distribution functions show that the solvent molecules of low diameter favour the counter ion adsorption on the electrode. With increasing diameter of the solvent molecules, the mean electrostatic potential increases, while the integral and differential capacitances decrease. The integral capacitance curves obtained by MPB theory are in qualitative agreement with those obtained by the GCMC simulation although the theoretical results are overestimated.

Solvent Molecule Bondability and Effect on Mechanical Proteins Transition State and Stability - A Smd Study

The solvent environment plays an integral role in physiological processes in the living cell. Changes in solvent environment or properties are a chemical signal that may induce changes in the mechanical response in a protein system. In this steered molecular dynamics study, using simulations we stretch to unfold the mechanical protein titin in aqueous and non-aqueous environment and reveal the atomic details and mechanism of interactions between solvent and proteins when subjected to steering force. Titin is a mechanically stable protein which is able to resist force due to a force bearing topology element - antiparallel beta sheet, stabilized by 6 native hydrogen bond contacts. In our study we observe individual solvent molecules bridging the stabilizing native hydrogen bonds in the force bearing patch. Solvent molecules also modulate the distance to the transition state. We investigate the distance to transition state of the unfolding reaction as related to solvent molecule size and we also introduce the concept of solvent molecule bondability - the capability of a solvent molecule to bridge the native hydrogen bond contact in more than one way, as determined by solvent molecule polarity and topology. Features of the simulations were also matched with previously reported experimental results.Since The distance to transition state determines the mechanical stability of a protein, changing the solvent composition is a novel way to fine tune mechanical properties. Our investigation provides insights of the properties of the unfolding reaction pathway and possible mechanisms of mechanical protection when such proteins are subject to mechanical stress.