Thermodynamic Interaction Parameters Research Articles

Investigation of electrochemical properties of lithium salt/poly(vinylidene fluoride)/polypyrrole blends

AbstractIn this study, structural, thermal, morphological, and electrochemical properties of poly(vinylidene fluoride)/polypyrrole (PVDF/PPy) blends are investigated. The investigation revealed phase separation between PPy and PVDF, a phenomenon supported by the thermodynamic interaction parameter. Increasing the PPy content from 10 to 50 wt% led to a significant reduction in the crystallinity of PVDF from 55.1% to 39.6%, and a corresponding decrease in the glass transition temperature (Tg) from 52.2 to 42.3°C. The enhanced interaction between components in the PVDF/PPy blends leads to an increase in local free volume due to the disruption of the polymer matrix. This disruption allows for greater molecular mobility, which in turn decreases the Tg. The increase in local free volume facilitates segmental motion of the polymer chains, thereby reducing the energy required for the transition from a glassy to a rubbery state. Ionic conductivity of the blends decreased with rising temperatures, likely due to interactions between the fluorine groups of PVDF and the NH groups of PPy. Notably, the transference number of lithium ions (tLi+) decreased from 0.30 to 0.14 as the PPy content increased from 10% to 50%, indicating a strong interaction between the cation and the polymer matrix.Highlights Electrochemical properties of poly(vinylidene fluoride)/polypyrrole (PVDF/PPy) blends are investigated. Interaction parameter‐supported phase separation is seen between PPy and PVDF. Intramolecular interactions of PVDF result in increasing local free volume. Ionic conductivity of the blends decreased with rising temperatures. tLi+ decreased with PPy increasing due to strong interaction of cation/matrix.

Investigating the electrochemical properties of poly(vinylidene fluoride)/polyaniline blends doped with lithium-based salt

Conductive polymers have attracted much attention in various applications, owing to their excellent chemical, thermal, and oxidative stability. However, they have low dielectric constant, which limits their performance in electrochemical devices. To overcome this drawback, blending with other polymers helps improving their electrochemical properties. Herein, we investigate structural and electrochemical properties of poly (vinylidene fluoride) (PVDF)/polyaniline (PANI) blends doped with lithium-based salt. Results showed that the blends exhibit phase separation of PANI and PVDF, which is confirmed by the thermodynamic interaction parameter. We found that the interaction between the two polymers enhanced the ionic conductivity from 4.9 × 10−5 S cm−1 for neat PVDF to 5.3 × 10−4 S cm−1 for composition of 50:50 (PANI50), whereas the ionic conductivity was inversely proportional to the temperature. Moreover, by adding lithium salt to the blend, the thermal stability increased from 376.6 to 478.5 °C for PANI50. The ionic conductivity of the blends depends on the PVDF content, which affects the interaction between the two polymers.

Separation of 2-ethoxyethanol from wastewater by four esters: Correlation of LLE thermodynamic modeling, influence of molecular structure, and investigation of component interactions

To prevent the wastewater containing 2-ethoxyethanol (2EE) from causing environmental pollution and economic waste, liquid–liquid extraction was used to recover 2-ethoxyethanol from wastewater in this study. The liquid–liquid equilibrium behavior of water + 2-ethoxyethanol + four solvents (propyl acetate, isopropyl acetate, n-butyl acetate, and isobutyl acetate) was investigated at 303.2 K and atmospheric pressure. The distribution coefficient (D) and separation factor (S) were used to compare and discuss the extraction efficiency of each system. The results indicated that all esters could effectively separate 2-ethoxyethanol from water. Among them, isobutyl acetate exhibited the highest values for D and S, demonstrating its superior separation capability. The experimental data were correlated with the thermodynamic model and interaction parameters were obtained. These parameters were verified using the GUI-MATLAB tool, and all four systems passed validation, confirming the reliability of the obtained binary interaction parameters. Furthermore, the root mean square deviation (RMSD) was used to assess the deviation between the experimental and regression values. The RMSD values for the NRTL and UNIQUAC models were 0.008 and 0.007, respectively. The interactions between 2-ethoxyethanol and water or esters were explored using σ-Profile, and it was found that esters with a branched chain structure provided better extraction. To explain the properties of the extractants microscopically, the interaction energies between 2-ethoxyethanol molecules and water or ester molecules, as well as the non-bonding energies of 2-ethoxyethanol in different media, were calculated.

Preferential Solvation Phenomena as Solute-Induced Structure-Making/Breaking Processes: Linking Thermodynamic Preferential Interaction Parameters to Fundamental Structure Making/Breaking Functions.

In this work, we identify the explicit macroscopic-to-microscopic rigorous links between existing thermodynamic preferential interaction parameters and microstructural descriptors based on total correlation function integrals, leading to their unambiguous characterization in terms of fundamental structure making/breaking functions . First, we provide the statistics mechanical framework to identify a universal molecular-based signature for the preferential solvation phenomenon involving solutes at infinite dilution in mixed-solvent environments and discuss its fundamental properties. Then, we characterize the functions relevant to the process, identify the microscopic markers for the existing preferential interaction parameters in terms of the functions, and test their compliance with a pair of essential microstructural constraints linked to the properties of the universal signature. Moreover, we illustrate the analysis by probing the behavior of a representative ternary system comprising the solubility of methane in aqueous 1,4-dioxane mixed-solvent environments under ambient conditions. Finally, we discuss some relevant issues surrounding the statistical mechanical (microstructural) interpretation of the thermodynamic (macroscopic) preferential interaction parameters, review some pitfalls in their evaluation from molecular simulation, and provide an outlook.

Thermodynamics of interactions and structural peculiarities of interpenetrating polymer networks based on polyurethane and copolymer of 2-hydroxyethyl methacrylate with methacryloyloxyethylphosphorylcholine

Interpenetrating polymer networks based on biocompatible components – polyurethane and copolymer of 2-hydroxyethyl methacrylate with methacryloyloxyethylyphosphorylcholine (HEMA-MPC) were synthesized and thermodynamic parameters of interactions in the system and morphology were investigated. The thermodynamic parameters of interactions between polymer components of the IPNs were calculated based on sorption isotherms of methylene chloride vapors by samples of the created polymer systems. It is shown that MPC plays the role of a compatibilizer in the system, increasing the thermodynamic compatibility between polyurethane and the HEMA-MPC copolymer at small amounts of the copolymer in the IPNs. As the amount of copolymer HEMA-MPC in the IPNs increases, the value of the free energy of the polyurethane and copolymer mixing shifts to the positive value, which is associated with the formation of ionic clusters of MPC. This may mean that with an increasing amount of the MPC in the system, interactions between the negatively charged phosphoryl groups and the positively charged nitrogen atom of various MPC polymer chains occur, i.e., the part of intermolecular interactions (polyurethane and copolymer) decreases, while the part of intramolecular interactions (between different groups of MPC) increases. The results of the morphology investigations of the IPN samples are consistent with the data of the thermodynamic compatibility study of polymers during the formation of the IPNs. With a significant increase in the positive values of the free energy of the polyurethane and copolymer mixing in the IPNs with 41 % and 51 % of the copolymer content, a significant phase separation is observed in the IPNs, with phase inclusions ranging from 1 to 5 mm.

Al–Ni–Ti thermodynamic database from first-principles calculations

First-principles calculations have increasingly become an essential tool for providing additional thermodynamic data for assessing thermodynamic databases using the CALPHAD methodology. As computational power increases and becomes easily accessible, first-principles calculation results have become more presented along with the experimental procedures to determine the thermochemical properties of the phases within a target system. This can help accelerate the alloy development process, even in complex multi-component systems. By using only first-principles calculation data for the both thermodynamic description and interaction parameters of end-members, an Al–Ni–Ti ternary thermodynamic database is constructed. By relying on the existing materials database for ground state stability of the known compounds, the constructed Al–Ni–Ti thermodynamic database can mostly capture all the features related to the solid-state phases appear in the ternary phase diagram comparable to that of the published database from an experimental data assessment.

Phase Transitions and Thermodynamic Interaction Parameters of Components in Poly(methyl methacrylate) and Poly(vinyl acetate)

Phase Transitions and Thermodynamic Interaction Parameters of Components in Poly(methyl methacrylate) and Poly(vinyl acetate)

The Thermodynamic Fingerprints of Ultra-Tight Nanobody-Antigen Binding Probed via Two-Color Single-Molecule Coincidence Detection.

Life on the molecular scale is based on a versatile interplay of biomolecules, a feature that is relevant for the formation of macromolecular complexes. Fluorescence-based two-color coincidence detection is widely used to characterize molecular binding and was recently improved by a brightness-gated version which gives more accurate results. We developed and established protocols which make use of coincidence detection to quantify binding fractions between interaction partners labeled with fluorescence dyes of different colors. Since the applied technique is intrinsically related to single-molecule detection, the concentration of diffusing molecules for confocal detection is typically in the low picomolar regime. This makes the approach a powerful tool for determining bi-molecular binding affinities, in terms of KD values, in this regime. We demonstrated the reliability of our approach by analyzing very strong nanobody-EGFP binding. By measuring the affinity at different temperatures, we were able to determine the thermodynamic parameters of the binding interaction. The results show that the ultra-tight binding is dominated by entropic contributions.

Binding Study of Antibacterial Drug Ciprofloxacin with Imidazolium-Based Ionic Liquids Having Different Halide Anions: A Spectroscopic and Density Functional Theory Analysis.

Herein, we have shown the interaction of an antibiotic drug ciprofloxacin (CIP) with three surface-active ionic liquids (ILs), having the same cation and different anions, namely, 1-decyl-3-methylimidazoliumtetrafluoroborate [C10mim][BF4], 1-decyl-3-methylimidazolium bromide [C10mim][Br], and 1-decyl-3-methylimidazolium chloride [C10mim][Cl]. This study has been performed by exploiting various spectroscopic techniques such as steady-state fluorescence, time-resolved fluorescence, and UV-visible spectroscopy. The fluorescence emission study of CIP with ILs was performed at various concentrations of all the three ILs. The emission spectra of CIP decreased in the presence of ILs, suggesting complex formation between CIP-IL. The effect of different concentrations of ILs on the emission spectra of CIP was exploited in terms of quenching and binding parameters. Further, fluorescence emission study was validated by the time-resolved fluorescence technique by measuring the average lifetime (τavg) of CIP in the presence of all the three ILs. The τavg value of the drug changed with the addition of ILs, which suggests complex formation between the drug and ILs. This complex formation was also confirmed by UV-visible spectroscopy results of CIP with all the three ILs. Further, for evaluating the thermodynamic parameters of the CIP-IL interactions, isothermal titration calorimetry (ITC) was performed. The ITC experiment yielded the thermodynamic parameters, ΔH (change in the enthalpy of association), ΔG (Gibbs free energy change), ΔS (entropy change), and binding constant (Ka). The binding parameters driven by ITC revealed that CIP-IL interactions are spontaneous in nature and enthalpy-driven, involving hydrophobic forces. Further, the classical density functional theory (DFT) calculations were performed, which provided deep insight for CIP-IL complex formation.

THERMODYNAMICS, MORPHOLOGY AND DYNAMIC-MECHANICAL PROPERTIES OF POLYURETHANE AND NANOCOMPOSITES BASED ON IT, CONTAINING HYDROXY-POSS

Nanocomposites based on polyurethane matrix consisting of an adduct of trimethylolpropane with toluene diisocyanate and a bifunctional polyester of poly(diethylene glycol) adipinate with mol. weight 2000, and contained 1,2-propanediolisobutyl-POSS with the amount of 1–10 %, were synthesized. The thermodynamic compatibility, dynamic-mechanical properties and morphology of the created nanocomposites were investigated. For the purpose of calculations the thermodynamic parameters of interactions between the components of POSS-containing nanocomposites, a study of the isothermal sorption of methylene chloride vapors by the created systems was conducted. The sorption of methylene chloride vapors by the samples of the native PU, POSS-containing nanocomposites and nanofiller was studied using a vacuum instalation with McBean balances. The values of the free energy of polyurethane and POSS mixing during the formation of the nanocomposites were calculated based on the concentration dependences of Ägm - the average free energy of mixing of individual components (polyurethane and POSS) and nanocomposites with methylene chloride, according to the thermodynamic cycles proposed by A.A. Tager. It is shown that polyurethane and hydroxy-POSS demonstrate thermodynamic incompatibility during the formation of nanocomposites. The free energy of mixing polyurethane and hydroxy-POSS have positive values at all concentrations of the nanofiller. By the method of dynamic-mechanical analysis investigations it was shown that the introduction of POSS into polyurethane matrix led to a shift of the tan δ maximum in the direction of increasing temperatures. The temperature values of the tan δ peak for nanocomposites with increasing POSS content increased from 38 to 47 °C for PU1 and PU10, respectively. With the introduction of the POSS nanofiller into the polyurethane matrix, the intensity of the tan δ peak also decreased. Therefore, it was shown that the introduction of hydroxy-POSS into the polyurethane matrix leads to suppression of segmental motions in polyurethane, to an increase in the glass transition temperature of nanocomposites, and to an increase in the modulus of elasticity of nanocomposites compared to the native matrix. It is assumed that this happens due to the fact that the part of hydroxy-POSS, which was not incorporated into the polyurethane chain, is concentrated in the flexible segments of polyurethane as a nanofiller. When studying the morphology of the created nanocomposites using scanning electron microscopy, it was found that starting from a content of 3 % of hydroxy-POSS, it forms agglomerates of nanoparticles in the polyurethane matrix, which increase in size when the content of hydroxy-POSS increases.

Study of molecular interactions by nonequilibrium capillary electrophoresis of equilibrium mixtures: Originations, developments, and applications.

Molecular interactions play a vital role in regulating various physiological and biochemical processes in vivo. Kinetic capillary electrophoresis (KCE) is an analytical platform that offers significant advantages in studying the thermodynamic and kinetic parameters of molecular interactions. It enables the simultaneous analysis of these parameters within an interaction pattern and facilitates the screening of binding ligands with predetermined kinetic parameters. Nonequilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) was the first proposed KCE method, and it has found widespread use in studying molecular interactions involving proteins/aptamers, proteins/small molecules, and peptides/small molecules. The successful applications of NECEEM have demonstrated its promising potential for further development and broader application. However, there has been a dearth of recent reviews on NECEEM. To address this gap, our study provides a comprehensive description of NECEEM, encompassing its origins, development, and applications from 2015 to 2022. The primary focus of the applications section is on aptamer selection and screening of small-molecule ligands. Furthermore, we discuss important considerations in NECEEM experimental design, such as buffer suitability, detector selection, and protein adsorption. By offering this thorough review, we aim to contribute to the understanding, advancement, and wider utilization of NECEEM as a valuable tool for studying molecular interactions and facilitating the identification of potential ligands and targets.

Thermodynamic parameters of phenylglycine interaction with UO22+, La3+ and Zr4+

Phenylglycine interactions with (UO22+, La3+ and Zr4+) transition metal ions were studied at different ionic strengths and different temperature degrees applying Bjerrum’s method. The work determine and discuss both the thermodynamic stabilities and the degree of interactions left(acute{{text{n}}}right). Also the work calculate and discuss the thermodynamic parameters of interactions of phenylglycine with (UO22+, La3+ and Zr4+). The variables that govern the interaction between phenylglycine and the metal ions under investigation were related to the nature of the amino acid reactive species as well as to the nature of M+ such as the valence and radius of the ion. It was observed that reactions between the M+ and L− were the most likely to occur. It was determined that the pH values affect the degree of complex formation overline{{text{n}}} as well as the production of various reactive spices. When the range of degree of interaction was more than 0.5 and less than 1.15, forming 1:1 stoichiometric complex. Additionally, it was shown that the stability of the complexes produced between phenylglycine and MZ+ increased in the subsequent order, which was in good accord with the Irving–Williams order.

PLBD: protein-ligand binding database ofthermodynamic andkinetic intrinsic parameters.

We introduce a protein-ligand binding database (PLBD) that presents thermodynamic and kinetic data of reversible protein interactions with small molecule compounds. The manually curated binding data are linked to protein-ligand crystal structures, enabling structure-thermodynamics correlations to be determined. The database contains over 5500 binding datasets of 556 sulfonamide compound interactions with the 12 catalytically active human carbonic anhydrase isozymes defined by fluorescent thermal shift assay, isothermal titration calorimetry, inhibition of enzymatic activity and surface plasmon resonance. In the PLBD, the intrinsic thermodynamic parameters of interactions are provided, which account for the binding-linked protonation reactions. In addition to the protein-ligand binding affinities, the database provides calorimetrically measured binding enthalpies, providing additional mechanistic understanding. The PLBD can be applied to investigations of protein-ligand recognition and could be integrated into small molecule drug design. Database URL https://plbd.org/.

Redox- and pH-responsive alginate-based magnetic hydrogel: “Smart” drug delivery and protein corona studies

A redox- and pH-responsive magnetic hydrogel was designed and developed based on alginate (Alg) through double crosslinking approach for sustained and targeted delivery of doxorubicin (Dox). For this objective, Fe3O4 nanoparticles (NPs) were synthesized by a chemical co-precipitation method, and then their surfaces were modified using an amine-end capped silane coupling agent. Alginate was oxidized using sodium periodate. Then, an alginate-based pH- and redox-responsive magnetic hydrogel with and without Dox loading was synthesized by adding amine-modified Fe3O4 NPs and cystamine (Cys) moiety through “Schiff-Base” condensation followed by double crosslinking with CaCl2. Drug loading and encapsulation efficiencies were quantified as 3.4 ± 0.27 and 83 ± 2.7%, respectively. Drug release study by dialysis method approved pH- and redox-dependent drug release behavior. Interactions between hydrogel and human serum albumin (HSA) was investigated using spectroscopy techniques, and it was found that the developed hydrogel can interact strongly with HSA. The thermodynamic parameters of the protein-hydrogel interaction were also calculated, and it was revealed that interaction process is spontaneous and endothermic. The anti-cancer activity of the developed magnetic DDS was assessed against MCF7 cells by MTT assay. It was found that free Dox had a stronger cytotoxic effect in the first 24 and 48 h in comparison with Dox-loaded DDS, while after 72 h, the DDS showed higher anti-cancer activity, possibly due to the controlled release of drug by the hydrogel over time.

Volumetric and conductivity studies of the interaction between levocetirizine dihydrochloride and the amino acids l-alanine and l-glutamine in aqueous solutions

Levocetirizine dihydrochloride (LCTZ) is a second-generation antihistamine known for its efficacy without sedation. However, the binding mechanism with plasma protein which makes it devoid of sedative effects is yet to be uncovered. In this study, we elucidated thermodynamic parameters of solute-solvent and solute-cosolute interactions between LCTZ, and the amino acids l-alanine (Ala) and l-glutamine (Gln) in aqueous solutions. The volumetric and conductance parameters were calculated using the experimental density and conductance data of aqueous solutions of Ala and Gln (concentration range of 0.02–0.20 mol kg−1) and LCTZ (concentration range of 0.01, 0.07, and 0.13 mol kg−1) at 298.15, 303.15, 308.15, and 313.15 K. Volumetric analysis study revealed that the apparent molar volume (Vφ), limiting apparent molar volume (Vφ0), and Masson's coefficient (Sv) values indicated predominantly solute-solvent interactions that were influenced by the solute's concentration and temperature. Meanwhile, partial molar expansibilities (Eφ0), transfer volume ΔtrVφ0 and Hepler's constant (δ2V0/δT2) established the solution system's structure-breaking tendency. The Gibb's free energy (ΔG0) values derived from conductometry data indicated the system's spontaneity. These calculated constants provided a detailed understanding of the different types of intermolecular interactions found in the ternary (LCTZ + water + amino acids) system.

Does the protein structure of β-lactoglobulin impact its complex coacervation with type A gelatin and the ability of the complexes to entrap lutein?

The heteroprotein complex coavervation (HPCC) is triggered by the interaction between oppositely charged proteins resulting in two liquid phases in equilibrium: the coacervate phase, which is rich in protein and the equilibrium solution which has low protein concentration. Several intrinsic and extrinsic factors affect the HPCC, including the nature and the conformational state of the involved proteins. In this work, the mechanism of complex coacervation between type A gelatin (GA) and native and thermal treated (70 °C/5 min) β-lactoglobulin (β-lg and β-lg (TT)) was investigated. In addition, the ability of the obtained complex coacervates to entrap lutein was evaluated. The applied thermal treatment led to an increase of about 20% in the concentration of surface free sulfhydryl groups and increased around 66% the surface hydrophobicity of β-lg (TT), compared with the untreated one. Nevertheless, minor impact was noticed in the aggregation state of the proteins, as well as in their ability to bind lutein (Ksv in the magnitude order of 104 M−1). The optimal condition for the complex coacervation between GA-β-lg and GA-β-lg (TT) was pH 6.5, minimal ionic strength and mass ratio of 2.5:1. Even if the applied thermal treatment did not promote important changes in the thermodynamic parameters of the molecular interaction between GA-β-lg (TT) compared with those for the molecular interaction between GA-β-lg, it negatively affected the coacervation yield (from 64% to 57% in the optimal condition). Both obtained complex coacervates exhibited high lutein entrapment efficiency, demonstrating their potential for protecting and delivering this bioactive compound.

From speciation study to removal of Pb2+ from natural waters by a carnosine-based polyacrylamide/azlactone copolymer

A deep speciation study on L-carnosine (CAR) and Pb2+ system was performed in aqueous solution with the aim to assess its potential use as a sequestering agent of metal cation. To determine the best conditions for Pb2+ complexation, potentiometric measurements were carried out over a wide range of ionic strength (0.15 ≤ I/≤ 1 mol/L) and temperature (15 ≤ T/°C ≤ 37), and thermodynamic interaction parameters (logβ, ΔH, ΔG and TΔS) were determined. The speciation studies allowed us to simulate sequestration ability of CAR toward Pb2+ under different conditions of pH, ionic strength and temperature and to establish a priori the conditions for the best removal performance, i.e., pH > 7 and I = 001 mol/L. This preliminary investigation was very useful in optimizing removal procedures and limiting subsequent experimental measurements for adsorption tests. Therefore, to exploit the binding ability of CAR for Pb2+ removal from aqueous solutions, CAR was covalently grafted on an azlactone-activated beaded-polyacrylamide resin (AZ) using an efficient click coupling reaction (78.3% of coupling efficiency). The carnosine-based resin (AZCAR) was analyzed by ThermoGravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA). Morphology, surface area and pore size distribution were studied through a combination of Scanning Electron Microscope (SEM) and adsorption/desorption of N2 analyses according to the Brunauer-Emmett-Teller (BET) and Barret-Johner-Halenda (BJH) approaches. The adsorption capacity of AZCAR toward Pb2+ was investigated under conditions simulating the ionic strength and pH of different natural waters. The time needed to reach equilibrium in the adsorption process was 24 h, and the best performance was obtained at pH > 7, typical of most natural waters, with removal efficiency ranging from 90.8% (at I = 0.7 mol/L) to 99.0 (at I = 0.001 mol/L).

Single-Molecule Analysis of SARS-CoV-2 Binding to C-Type Lectin Receptors.

Despite intense scrutiny throughout the pandemic, development of efficacious drugs against SARS-CoV-2 spread remains hindered. Understanding the underlying mechanisms of viral infection is fundamental for developing novel treatments. While angiotensin converting enzyme 2 (ACE2) is accepted as the key entry receptor of the virus, other infection mechanisms exist. Dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) and its counterpart DC-SIGN-related (DC-SIGNR, also known as L-SIGN) have been recognized as possessing functional roles in COVID-19 disease and binding to SARS-CoV-2 has been demonstrated previously with ensemble and qualitative techniques. Here we examine the thermodynamic and kinetic parameters of the ligand-receptor interaction between these C-type lectins and the SARS-CoV-2 S1 protein using force-distance curve-based AFM and biolayer interferometry. We evidence that the S1 receptor binding domain is likely involved in this bond formation. Further, we employed deglycosidases and examined a nonglycosylated S1 variant to confirm the significance of glycosylation in this interaction. We demonstrate that the high affinity interactions observed occur through a mechanism distinct from that of ACE2.

Empirical modeling of the bandgap energies of CdxZn1−xS in the full x-ratio range from ZnS to CdS

The bandgap energy of CdxZn1-xS at any given mole composition x in CdS is estimated by using, for the first time, the Redlich-Kister expression to examine the deviation to the linearity, for determining the corresponding thermodynamic interaction parameters, and interpret the sign of deviation to the linearity considered as ideal behavior. The current study introduces, for the first time, the concept of reduced Redlich-Kister function QY,T(xi) to bring to light the importance of interaction due to the progressive introduction of Cd into the pseudo-binary CdxZn1-xS and to reveal eventual specific characteristics of the studied pseudo-binary CdxZn1-xS. For the first time, as different from the bandgap energies EgCdS and EgZnS of the pure binary semiconductors ZnS and CdS, respectively, the concept of current bandgap energies Egc1(x) and Egc2(x) of each component CdS (1) and ZnS (2) within the system, respectively, is introduced. It indicates the effective individual contribution within the pseudo-binary CdxZn1-xS system at the given molar composition (x) of CdS. The study reveals that the concept of current bandgap energy is thermodynamically equivalent to the partial molar quantity, interesting to reveal the individual and effective contribution of Cd and Zn into the pseudo-binary CdxZn1-xS at a given mole composition (x).

Water-Tree Characteristics and Its Mechanical Mechanism of Crosslinked Polyethylene Grafted with Polar-Group Molecules.

In order to restrain electric-stress impacts of water micro-droplets in insulation defects under alternating current (AC) electric fields in crosslinked polyethylene (XLPE) material, the present study represents chemical graft modifications of introducing chloroacetic acid allyl ester (CAAE) and maleic anhydride (MAH) individually as two specific polar-group molecules into XLPE material with peroxide melting approach. The accelerated water-tree aging experiments are implemented by means of a water-blade electrode to measure the improved water resistance and the affording mechanism of the graft-modified XLPE material in reference to benchmark XLPE. Melting–crystallization process, dynamic viscoelasticity and stress-strain characteristics are tested utilizing differential scanning calorimeter (DSC), dynamic thermomechanical analyzer (DMA) and electronic tension machine, respectively. Water-tree morphology is observed for various aging times to evaluate dimension characteristics in water-tree developing processes. Monte Carlo molecular simulations are performed to calculate free-energy, thermodynamic phase diagram, interaction parameter and mixing energy of binary mixing systems consisting of CAAE or MAH and water molecules to evaluate their thermodynamic miscibility. Water-tree experiments indicate that water-tree resistance to XLPE can be significantly improved by grafting CAAE or MAH, as indicated by reducing the characteristic length of water-trees from 120 to 80 μm. Heterogeneous nucleation centers of polyethylene crystallization are rendered by the grafted polar-group molecules to ameliorate crystalline microstructures, as manifested by crystallinity increment from 33.5 to 36.2, which favors improving water-tree resistance and mechanical performances. The highly hydrophilic nature of CAAE can evidently inhibit water molecules from aggregating into water micro-droplets in amorphous regions between crystal lamellae, thus acquiring a significant promotion in water-tree resistance of CAAE-modified XLPE. In contrast, the grafted MAH molecules can enhance van der Waals forces between polyethylene molecular chains in amorphous regions much greater than the grafted CAAE and simultaneously act as more efficient crystallization nucleation centers to ameliorate crystalline microstructures of XLPE, resulting in a greater improvement (relaxation peak magnitude increases by >10%) of mechanical toughness in amorphous phase, which primarily accounts for water-tree resistance promotion.