Interaction Of Polar Groups Research Articles

A novel insight of interaction mechanism of carboxymethyl cellulose with talc surface: A combined molecular dynamic simulation and DFT investigation

Separation of talc from sulfide minerals through adding depressor in flotation field is very necessary, while the interaction of depressor on the surface of talc still needs to be further explained. Here, a typical depressor, carboxymethyl cellulose (CMC), interacted with talc surface was deeply investigated from atomic structure and surface hydration though molecular dynamic simulation (MDs) and density functional theory (DFT) calculation. MDs was applied on investigating adsorption behaviors of CMC on basal and edge plane of talc in aqueous solutions, and DFT was used for studying the interacted orbitals and charge transfer. It was found that adsorption of CMC on surface of edge plane was stronger than that on the surface of basal plane due to the enhanced interaction of polar group on the edge plane and the dragged water molecules. Interactions existed between H atoms in CMC and O atoms in edge plane, between O atoms in CMC and Si, Mg atoms in edge plane. The strong interacted water molecules dragged CMC close to the surface, thus to strengthen the binding of CMC and edge plane of talc. Furthermore, the hydration shell on the basal and edge plane of talc was investigated for explaining the phenomenon. Therefore, our work gave a new insight into the microscopic interaction between talc and CMC, thus to guide the actual application.

A ternary cross-linked gel electrolyte with high mechanical strength and ionic conductivity for ultra-long-life reversible zinc deposition

Bottlenecks such as electrolyte leakage, zinc dendrite growth, and poor mechanical properties severely limit practical application of aqueous zinc ion batteries. To improve the cycle stability and reversibility of zinc deposition in zinc ion batteries, a ternary cross-linked gel electrolyte PCS composed of polyacrylamide, carboxymethyl cellulose and soluble starch was designed. The solid ternary cross-linked structure provides excellent mechanical properties of PCS gel. The interaction of polar groups with H2O and Zn2+ significantly reduced the activity of the mobilized water in PCS, inhibiting the occurrence of side reactions, and regulating the solvation structure of Zn2+. As a result, the cells with PCS have ultra-long-life reversible zinc deposition (stable cycling of Zn//Zn symmetric cells over 4900 h), high reversibility (coulombic efficiency of 99.5%) and high cycling stability (cycling stably for 1000 cycles).

MOLECULAR COMPLEXES OF MONOAMMONIUM SALT OF GLYCYRRHIZIC ACID WITH SOME UREA AND THEIR ANTIBIOTIC ACTIVITY

This article reports on obtaining the inclusion compounds of the monoammonium-glycyrrhizin salts with urea, thiourea and methylolthiourea. The compounds were obtained by the liquid phase way, and their structures were characterized by the UV- and IR-Spectroscopic methods. Proceeding from the spectral data, it was concluded that the complexation occurs through the interaction of polar groups of the components. The composition of the complexes was studied using the method of isomolar series. Equilibrium constants and changes in Gibbs free energy of the complexation process were also calculated. The biological activity of complex compounds was studied on the example of fungicidal activity of one of the most common pathogenic fungus Fusarium. The obtained compounds can be used as as fungicides and stimulants in agriculture.

Influence of Alkyl Sidechain Length on Lithium-Ion Conductivity for Polyether Electrolytes

Lithium-ion batteries (LIBs) have been used in various energy devices, from small electronic devices to electric vehicles. However, LIBs have safety concerns, mainly due to the flammable organic solvents used for electrolytes. The development of electrolytes based on flame-retardant materials, including polymer, is one of the potential solutions. Although various polymer electrolytes (PEs) were successfully synthesized, the low lithium-ion (Li+) conductivity hinders its practical application.It is considered that the Li+ conductivity in PEs is determined by two factors; (i) segmental mobility of polymer chains and (ii) Li+ concentration, which is connected to the Li+ mobility and the number of ion carriers, respectively. Most of the PEs failed to meet those requirements, which hinders the improvement of Li+ conductivity. The problem is that the polar groups in the polymer chains tend to actively coordinate with Li+ under high Li+ concentration, which inhibits the mobility of the polymer chains. Also, the Li+-polar group interaction anchors Li+ on the polymer chain, which may also suppress the Li+ conductivity.Therefore, to establish a polymer design strategy, it is necessary to elucidate the factors which affect the interaction between Li+-polar groups and Li+ transportation. Previous studies have focused mainly on the polar properties (e.g., donor number and dielectric constant) of the polymers to understand the interaction between Li+ and polar groups. In contrast, the effect of non-polar groups was often overlooked. Non-polar groups can affect the mobility and polarity of polymers as well as the Li+-polar group interaction, due to its plasticization effect, polarity, and steric hindrance.Here, in this study, we selected polyethers having alkyl sidechains with different lengths (–(CH2)m–H, m = 1, 2, 4, 6, 8, and 12), to clarify the contribution of the non-polar groups on the Li+ conductivity in PEs. Electrochemical impedance spectroscopy revealed that the ionic conductivity (σ) at low temperatures was dominated by glass transition temperature, which correlates with the segmental mobility of polymer chains. Furthermore, σ increase with the increase in the length of the alkyl group due to the internal plasticization effect of the long alkyl groups. On the contrary, the σ at high temperature was mostly determined by salt dissociation capacities of polymers, which tended to increase as the alkyl group became shorter. The Li+ transportation number (t Li+) gradually improved with the extension of the alkyl groups; 0.16 (m = 1) < 0.26 (m = 2) < 0.28 (m = 4) < 0.32 (m = 6) < 0.36 (m = 8) < 0.43 (m = 12). We believe that the gradual changes of t Li+ are due to the low polarity of long alkyl sidechain, giving low dielectric constant and/or low viscous properties. The activation energy of Li+ transportation at the electrode-electrolyte interface (E int) showed a large gap between m =1 and others; E int = 68–82 kJ mol–1 (m = 2, 4, 6, 8, and 12) < E int = 116 kJ mol–1 (m = 1). The coordination number of ether groups (n ether) estimated from ν(COC) intensity of infrared spectra showed a similar trend; n ether = 3.6–4.4 (m ≥ 2) < n ether = 6.2 (m = 1). The interaction between the ether group and Li+ can be affected by the length of alkyl sidechain, and it effectively suppressed for alkyl sidechain of m > 1, probably because of the steric hindrance. Considering the similar trend in both E int and n ether, the amount of ether-Li+ interaction can be a descriptor to determine Li+ transportation at the electrode-electrolyte interface.In summary, the Li+ conductivity, including ionic conductivity (σ) and Li+ transportation number (t Li+) strongly influenced by the properties of the alkyl group, such as the internal plasticization effect and low polarity. The Li+-ether group interaction, which was governed by the steric hindrance of alkyl sidechain, can be a dominant factor for the activation energy of Li+ transportation at the electrode-electrolyte interface (E int). Designing alkyl sidechains is thus a valid strategy to optimize segmental mobility and polarity of the bulk as well as the local interaction at the interface, which leads to the improved Li+ conductivity at bulk and electrode-electrolyte interfaces.

Pair interaction energy decomposition analysis (PIEDA) and experimental approaches for investigating water interactions with hydrophilic and hydrophobic membranes

The origins of low and high interactions of polar groups with water molecules are still unknown and need to be further examined for effective future membrane synthesis and modification. The primary aim of this research study is to provide a comprehensive overview of the interactions at the molecular level occurring between water molecules and the fragments of hydrophobic and hydrophilic membranes based on pair interaction energy decomposition analysis (PIEDA) as part of the fragment molecular orbital (FMO) method’s framework. This direction is critical, since a research study of the reasons for water and membrane interactions can help design groundbreaking membranes with superior hydrophilicity characteristics. To accomplish this, the computational studies, the Polyvinylidene fluoride (PVDF [H(–CH2–CF2–)4CH3]) and Polyacrylonitrile (PAN [(H(–CH2–CH(CN)–)4CH3]) membranes were considered as models for hydrophobic and hydrophilic membranes, respectively. Density-functional theory (DFT), based on B3LYP functional and split-valance 6-311+G (d,p) basis sets, was used in order to optimize the geometry of PAN, PVDF, and their complexes with different numbers of water molecules. Furthermore, fragment molecular orbit (FMO) and the Pair Interaction Energy Decomposition Analysis (PIEDA) were carefully interrogated. These types of analyses included the inter fragment interaction energy (IFIE), like the electrostatic (ES), exchange repulsion (EX), charge-transfer and mixing term (CT + mix) energies. Furthermore, the hydrophilicity and hydrophobicity of the origins of membrane function groups were experimentally evaluated through Fourier-transform infrared spectroscopy (FTIR- ATR), 13C cross polarization magic angle spinning (13C CP MAS) Solid State Nuclear magnetic resonance SSNMR, and Fourier transform Raman (FT-Raman) spectroscopies. Confocal microscopic approach was used to interrogate water transport and the interactions between fluorescence particles and membrane layers. Furthermore, the Infrared (IR) spectroscopy was performed to investigate interaction between water molecules and PVDF and PAN. The theoretical results had a good agreement with experimental result.

Adsorption and Chromatographic Separation of Thiophene Derivatives on Graphitized Thermal Carbon Black

The thermodynamic characteristics of adsorption (TCA) of thiophene and its derivatives are determined under the conditions of equilibrium gas adsorption chromatography (GAC) on columns with graphitized thermal carbon black (GTCB) of Carbopack C HT grade. It is shown that the TCA values ​​ depend largely on the number and nature of the substituents in the main structural fragment. It is found that the surface of the GTCB is characterized by low structural selectivity for positional isomers in the series of thiophene derivatives. The effect of polar retention of an adsorbate on graphite from the gas phase due to additional intermolecular specific interactions of polar groups of the adsorbate with an easily polarizable surface of the base face of graphite is established and studied. Conclusions are reached on the applicability of the two-dimensional ideal gas model for describing the mobility of strongly polar molecules of thiophene derivatives on surfaces of graphite, and on the considerable limitations of this model when applied to the adsorption of thiophene molecules, along with its methyl and halogen derivatives.

Reactivity of fluoroalkanes in reactions of coordinated molecular decomposition

Experimental results on the coordinated molecular decomposition of RF fluoroalkanes to olefin and HF are analyzed using the model of intersecting parabolas (IPM). The kinetic parameters are calculated to allow estimates of the activation energy (E) and rate constant (k) of these reactions, based on enthalpy and IPM algorithms. Parameters E and k are found for the first time for eight RF decomposition reactions. The factors that affect activation energy E of RF decomposition (the enthalpy of the reaction, the electronegativity of the atoms of reaction centers, and the dipole–dipole interaction of polar groups) are determined. The values of E and k for reverse reactions of addition are estimated.

Reactivity of bromoalkanes in reactions of coordinated molecular decay

The results from experiments on reactions of the coordinated molecular decay of RBr bromoalkanes on olefin and HBr are analyzed using the model of intersecting parabolas (MIP). Kinetic parameters within the MIP are calculated from the experimental data, enabling calculation of the activation energies (E) and rate constants (k) of such reactions, based on the enthalphy of the reaction and the MIP algorithms. The factors affecting the E of the RBr decay reaction are established: the enthalphy of the reaction, triplet repulsion, the energy of radical R• stabilization, the presence of a π bond adjacent to the reaction center, and the dipole–dipole interaction of polar groups. The energy spectrum of the partial energies of activation is constructed for the reaction of coordinated molecular decay of RBr, and the E and k of inverse addition reactions are evaluated.

Impact of polar groups concentration and free volume on water sorption in model epoxy free films and coatings

Abstract The water sorption characteristics have been determined for two model epoxy systems based on the DGEBA resin and two amine hardeners (TETA and DAMP). A particular attention was paid to the curing protocol to control the macromolecular architectures. Using FTIR, DSC and DMTA measurements, it was demonstrated that both network microstructures differ mainly in the polar groups density, the potential crosslinking nodes and the free volume. DGEBA/DAMP system presents a higher free volume fraction and a lower polar groups concentration compared to the DGEBA/TETA system. Gravimetric measurements on free films and EIS experiments onto coated steel Q-panels were carried out to follow the water sorption kinetics at different temperatures (30, 40, 50 and 60 °C). For both epoxy systems, the diffusion processes follow a pseudo-fickian behaviour with two diffusive stages. Solubility and diffusion processes are discussed in relation with the microstructural specificities of the polymer networks using a thermodynamic framework. The main result is that in DGEBA/DAMP and DGEBA/TETA systems, the water diffusion and solubility are mainly governed by a water polar group interaction mechanism.

Effect of H2O and reduced graphene oxide on the structure and rheology of self-healing, stimuli responsive catecholic gels

A catechol-containing organogel based on random copolymers of N-isopropylacrylamide (NIPAM) and dopamine methacrylate (NIDO5%) in dimethyl formamide (DMF) was supramolecularly crosslinked by NaBH4 in the presence of reduced graphene oxide (RGO). The focus of the investigations was on the influence of H2O and RGO in the system, which leads to a softening and stiffening, respectively. Whereas RGO tends to restack partially, this tendency was not found in the gels, suggesting a surface coverage of RGO with NIDO5% due to H-bonding and surface crosslinking attributed to the interactions of polar groups of polymer chains with carboxylic and carbonyl groups of RGO sheets proven by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction and spectroscopy (XRD). While RGO leads to the system becoming more brittle, its presence does not lead to an excessive loss of the self-healing characteristics, but it clearly stabilizes the gel when swollen with H2O, as can be seen from the significantly higher modulus and the retained self-healing behavior.

Simulation of gelation process in cysteine–silver solution by dissipative particle dynamics method

The results of simulating gelation in a cysteine–silver solution have been presented. All calculations have been carried out in terms of the dissipative particle dynamics method. In the developed model, the introduction of a salt, which initiates gelation, is taken into account implicitly by setting the parameters of the interaction between polar groups of cysteine and a solvent. It has been shown that fibers of gel network are formed in a narrow range of the initiating salt concentration due to weakened interaction of polar groups of cysteine with a solvent.

Stretchable and Self-Healing Graphene Oxide–Polymer Composite Hydrogels: A Dual-Network Design

Superior mechanical properties and self-healing are two hot topics in hydrogel science due to their tight relationship with the following potential application scopes. Most of the conventional hydrogels do not possess both features at the same time. Herein, we expand the recently proposed intertwined double-network mechanism and prepare a novel class of graphene oxide (GO)/poly(acryloyl-6-aminocaproic acid) (PAACA) composite hydrogels with enhanced mechanical properties and self-healing capability to pH stimulus. Without the use of any conventional organic cross-linkers, the double networks in GO/PAACA hydrogels are triggered by GO nanosheets and calcium ions as cross-linkers. For one thing, Ca2+ induces the formation of the 3D cross-linked network through coordination interactions with both oxygen-containing groups of GO nanosheets and polar groups of PAACA side chains. For another, powerful hydrogen-bonding network is simultaneously interconnected, attributed to the interactions of polar groups of PAACA...

Effect of the acetate group content on gas permeation through membranes based on poly(ethylene-co-vinyl acetate) and its blends

The transport of gases through poly(ethylene-co-vinyl acetate) (EVA) of vinyl acetate (VAc) content ranging from 25 to 70wt%, and through the respective EVA blends was studied. The both types of materials exhibited the same order of decreasing permeability CO2>He>O2>N2. However, the membranes prepared from EVA copolymers were found to be more permeable than those obtained from the blends, showing a maximum of P value at 46wt% of VAc, while the composition dependence of P for the blends was observed to comply with a rule for miscible blends. The observed differences in permeation behavior were correlated with physical properties of the membrane materials such as density, Tg, crystallinity, and FFV. All the membranes studied exhibited high selectivities (α) for CO2/N2, and the low separation ability for O2/N2. The values of α for the blend materials were found to be larger than those for the copolymers with the same VAc content, and to increase more sharply with the increasing amount of VAc. These results indicate that polymer blends may offer advantages over single component polymer system in the approach of increasing membrane separation performance by using favorable interactions of polar groups with CO2.

Towards understanding hydrophobic recovery of plasma treated polymers: Storing in high polarity liquids suppresses hydrophobic recovery

The phenomenon of hydrophobic recovery was studied for cold air plasma treated polyethylene films. Plasma-treated polymer films were immersed into liquids with very different polarities such as ethanol, acetone, carbon tetrachloride, benzene and carbon disulphide. Hydrophobic recovery was studied by measurement of contact angles. Immersion into high polarity liquids slows markedly the hydrophobic recovery. We relate this slowing to dipole–dipole interaction of polar groups of the polymer with those of the liquids. This kind of interaction becomes decisive when polar groups of polymer chains are at least partially spatially fixed.

Synthesis and Properties of Dodecyl Trehaloside Detergents for Membrane Protein Studies

Sugar-based detergents, mostly derived from maltose or glucose, prevail in the extraction, solubilization, stabilization, and crystallization of membrane proteins. Inspired by the broad use of trehalose for protecting biological macromolecules and lipid bilayer structures, we synthesized new trehaloside detergents for potential applications in membrane protein research. We devised an efficient synthesis of four dodecyl trehalosides, each with the 12-carbon alkyl chain attached to different hydroxyl groups of trehalose, thus presenting a structurally diverse but related family of detergents. The detergent physical properties, including solubility, hydrophobicity, critical micelle concentration (CMC), and size of micelles, were evaluated and compared with the most popular maltoside analogue, β-D-dodecyl maltoside (DDM), which varied from each other due to distinct molecular geometries and possible polar group interactions in resulting micelles. Crystals of 2-dodecyl trehaloside (2-DDTre) were also obtained in methanol, and the crystal packing revealed multiple H-bonded interactions among adjacent trehalose groups. The few trehaloside detergents were tested for the solubilization and stabilization of the nociceptin/orphanin FQ peptide receptor (ORL1) and MsbA, which belong to the G-protein coupled receptor (GPCR) and ATP-binding cassette transporter families, respectively. Our results demonstrated the utility of trehaloside detergents as membrane protein solubilization reagents with the optimal detergents being protein dependent. Continuing development and investigations of trehaloside detergents are attractive, given their interesting and unique chemical-physical properties and potential interactions with membrane lipids.

Tailor-made fumed silica-based nano-composite polymer electrolytes consisting of BmImTFSI ionic liquid

In this work, nano-sized fumed silica (SiO2) was embedded in poly(methyl methacrylate) (PMMA)–poly(vinyl chloride) (PVC) blend with 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl imide) (BmImTFSI) as ionic liquid. These composite polymer electrolytes (CPEs) were prepared by solution casting technique. The samples followed Arrhenius behavior in the temperature-dependence of ionic conductivity and further proved the ionic hopping mechanism in the polymer electrolyte. It is suggested the formation of three-dimensional polymer network among the aggregates weakens the interaction of polar group of the polymer backbone and initiates the ionic decoupling process. The mobile ions from adjacent sites would occupy this vacant site and reform the interactive bond with the polymer backbone whereby the ionic hopping mechanism is generated. The activation energy (Ea) is further determined. The higher the ionic conductivity, the lower the activation energy. The maximum ionic conductivity of (8.26 ± 0.02) mScm−1 was achieved at 80 °C upon inclusion of 8 wt% of SiO2. X-ray diffraction (XRD) analysis revealed the higher amorphous region with increasing SiO2 mass loadings. The coherence length is further determined by using Debye–Scherrer equation. Higher amorphous region in the polymer matrix is conferred by showing the lower coherent length. Scanning electron microscopy (SEM) was applied to examine the morphology of polymer electrolytes. Based on the differential scanning calorimetry (DSC) study, glass transition temperature (Tg) and melting temperature (Tm) were decreased. Highly flexible polymer chain is produced when the Tg was lowered down. On the other hand, thermal stability of polymer electrolytes was increased by SiO2 dispersion, as depicted in thermogravimetric analysis (TGA).

Reinforcement of Ethylene-Propylene-Diene Rubber/Samarium Borate and Ethylene-Propylene-Diene Rubber/Sb-doped SnO2 Composites by Three Types of Ethylene—Acrylic Acid: Assessment of Acrylic Acid Content on Crystallinity, Cure, Mechanical, and Electric Properties

The aim of this study is to investigate the effect of acrylic acid (AA) content of ethylene—acrylic acid copolymers (EAA) and pH level of filler particles on reinforcement of peroxide-cured ethylene—propylene—diene rubber (EPDM)/samarium borate (SmBO3) and EPDM/ Sb-doped SnO 2 (ATO) composites. It was found that EAA could reinforce EPDM by both crystallization and hydrogen bonds formed among carboxyl groups at room temperature, whereas at 180°C EAA could melt and hydrogen bonds would dissociate, both of which could enhance fluidity of gum and facilitate the processing. During vulcanization, carboxylic acid groups could dehydrate among molecules to increase crosslink density. Moreover, the alkaline SmBO3 could neutralize the carboxyl acid and makes dicumyl peroxide more likely to decompose into radicals than in the presence of acidic ATO, which endows EPDM with more crosslink density. After vulcanization, reinforcement of EPDM could be affected by the interaction of crystallinity of EAA, the formed hydrogen bonds and the amount of crosslink points. Surface and volume resistivity of EPDM composites would be reduced because of more conductive channels caused by the rising AA content. Dielectric properties would be affected by the interaction of polar groups and crosslink density.

Model of the radical addition reaction as the superposition of three potential curves

A new semiempirical model of the reaction of radical addition to molecules with multiple bonds has been developed. In the framework of this model, the transition state (TS) of the reaction X. + Y=Z → XYZ. is considered as the result of the intersection of the potential curve of the stretching vibration of the forming bond X-Y with the curve that is the difference between the amplitudes of stretching vibrations of the Y-Z and Y=Z bonds and the stretching vibrations are considered harmonic. The kinetic parameters describing the activation energy as a function of the enthalpy of the reaction were calculated for 34 classes of addition reactions using the new model. The factors determining the activation energy of the addition reactions are analyzed: triplet repulsion in the TS, the π electrons in the α position to the reaction center, the electronegativity of atoms of the reaction center of the TS, the steric factor, the interaction of polar groups in the TS, and the force constants of the reacting bonds. The increments characterizing the contribution of these factors to the activation energy are calculated. The model is also used to describe the energy of 12 classes of cyclization reactions and 16 classes of radical decomposition reactions. The parameters that make it possible to estimate the activation energy of the reaction from its enthalpy are calculated for these classes of reactions.

Linear Adsorption of Nonionic Organic Compounds from Water onto Hydrophilic Minerals: Silica and Alumina

To characterize the linear adsorption phenomena in aqueous nonionic organic solute-mineral systems, the adsorption isotherms of some low-molecular-weight nonpolar nonionic solutes (1,2,3-trichlorobenzene, lindane, phenanthrene, and pyrene) and polar nonionic solutes (1,3-dinitrobenzene and 2,4-dinitrotoluene) from single- and binary-solute solutions on hydrophilic silica and alumina were established. Toward this objective, the influences of temperature, ionic strength, and pH on adsorption were also determined. It is found that linear adsorption exhibits low exothermic heats and practically no adsorptive competition. The solute-solid configuration and the adsorptive force consistent with these effects were hypothesized. For nonpolar solutes, the adsorption occurs presumably by London (dispersion) forces onto a water film above the mineral surface. For polar solutes, the adsorption is also assisted by polar-group interactions. The reduced adsorptive forces of solutes with hydrophilic minerals due to physical separation by the water film and the low fractions of the water-film surface covered by solutes offer a theoretical basis for linear solute adsorption, low exothermic heats, and no adsorptive competition. The postulated adsorptive forces are supported by observations that ionic strength or pH poses no effect on the adsorption of nonpolar solutes while it exhibits a significant effect on the uptake of polar solutes.

Interaction of Polar Groups with a Bulky Hydrocarbon Residue: Polarizability and Steric Effects

Energies of two series of branched hydrocarbon monosubstituted derivatives, 2-substituted 2-methylpropanes and 1-substituted bicyclo[2.2.2]octanes with 19 different substituents were calculated at the B3LYP/6-311+G(d,p) level and compared with the energies of straight-chain 1-substituted butanes. The comparison was carried out in terms of isodesmic homodesmotic reactions, in which the substituent is transferred from one hydrocarbon residue to another. The branched derivatives are mostly stabilized, in the extreme case by as much as 30 kJ mol-1 confirming that the additive rule used for estimating the enthalpies of formation is not valid for branched derivatives. The stabilization energies ∆E for the individual substituents X are not proportional to any known substituent parameters. In the qualitative respect, they are controlled by the first atom of the substituent - similarly as in the straight-chain isomers - but in the case of sterically demanding substituents they are perturbed by a destabilizing steric effect.