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To understand the occurrence of natural gas hydrates in seabed sediments, it is crucial to examine the mechanisms of methane (CH 4) hydrate formation in sodium montmorillonite (Na-Mt) systems in the presence of amino acid. Accordingly, this study employed kinetics experiments and molecular dynamics simulations to investigate CH 4 hydrate nucleation and growth in an Na-Mt system containing alanine (Ala), leucine (Leu), and phenylalanine (Phe), respectively. Kinetics and Raman experiments showed that, compared with Ala, Leu and Phe enhanced hydrogen bonding between water molecules surrounding Na-Mt. This enhancement was due to the long carbon chain of Leu and the phenyl ring of Phe and facilitated CH 4 hydrate formation. Moreover, in the Na-Mt system, Ala reduced CH 4 consumption, whereas Leu and Phe increased CH 4 consumption. Molecular dynamics simulations revealed that the strength of electrostatic interactions between the negatively charged Na-Mt surface and the functional groups of amino acids affected the distribution of amino acids, thereby altering CH 4 aggregation and CH 4 hydrate nucleation processes. The strong interaction between Na-Mt and Ala significantly disrupted interfacial interactions between Na-Mt and water molecules. In contrast, the weaker interactions between Na-Mt and Leu and Phe, respectively, meant that these amino acids affected CH 4 hydrate nucleation in the bulk-like solution by influencing the arrangement of water molecules. These findings indicate that interfacial interactions between Na-Mt and amino acids play a crucial role in CH 4 hydrate formation. Overall, this study generated insights into the formation kinetics and nucleation properties of CH 4 hydrates in clay mineral–amino acid complexes that may increase understanding about the occurrence of natural gas hydrates in marine sediments. • Kinetics experiments and simulations explored CH 4 hydrate formation in Na-Mt with amino acids. • Electrostatic interactions between Na-Mt surface and amino acids affect CH 4 aggregation and hydrate formation. • Leucine and phenylalanine stay in bulk solution, unlike alanine, which interacts more with the Na-Mt surface. • Leucine's carbon chain and phenylalanine's ring enhance hydrogen bonding among surrounding water molecules. [ABSTRACT FROM AUTHOR]

Wan and Zaoui (2024) conducted molecular dynamics simulations (MDS) to explore friction dynamics at the rubber-clay interface under the realm of rubber-soil mixtures (RSM). It's an interesting deviation from the regular RSMs wherein rubber-sand mixtures only have been considered so far. However, it should be noted that the mixing of rubber with clays would result in the creation of heterogeneous mixtures. Furthermore, Wan and Zaoui (2024) have overlooked the effect of moisture, which, in the case of clays, and especially in the case of sodium-montmorillonite, will influence the shearing (which the authors have referred to as sliding) behavior and thus, the friction dynamics. Furthermore, the influence of horizontal stresses and/or confinement, excess pore-water pressure, and interfacial deformation on the RSM have been overlooked, which limit the applicability of the work for the 'dynamic loading conditions'. These issues emphasize the necessity of a broader perspective on the material properties (viz., particle size, specific gravity, etc.) and environmental influences (viz., loading conditions, moisture, etc.) within RSM, and thus, considering these issues might help in enhancing the scientific understanding and future research in this area. [ABSTRACT FROM AUTHOR]

Innovations in sophisticated optoelectronic devices have increased interest in high-refractive index polymers. Herein, we report innovative nanocomposite films with high linear and nonlinear refractive indices prepared by casting chitosan (Cs) with polyvinyl alcohol (PVA) (50:50 wt%) along with different concentrations (10–50 wt%) of sodium montmorillonite (NaMMT) nanoclay. The refractive indices in addition to other optical parameters of homopolymers and hybrid materials were investigated by UV–Vis. spectroscopy and optical modeling to assess their potential applications in optics. Besides, the structure, morphology, and thermal stability of the prepared films were investigated by a multitude of experimental techniques including X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA/DTG). The ATR-FTIR, XRD, SEM, and AFM measurements confirmed the complete exfoliation of NaMMT nanolayers in the Cs/PVA matrix. The TGA/DTG revealed an increase in the thermal stability of Cs/PVA film with increasing clay content. The UV–Vis. measurements revealed a decrease in the optical energy gap (E g) and a substantial increase in the linear (n D) and nonlinear (n 2) refractive indices as clay content increased. Additionally, the nanohybrids displayed low UV transmission and reflected about 80 % of UV rays, making them excellent candidates for UV protection. For the first time, the dissipation factor (tan δ) in the UV/Vis. region has been calculated and fitted with the Drude-Lorentz model to predict the plasma frequency (ω p), resonance frequency (ω 0), and electron lifetime (τ) of pristine polymers and nanocomposites. [Display omitted] • Cs/PVA/NaMMT nanocomposite films were prepared by casting method. • Structure analyses revealed complete exfoliation of NaMMT in Cs/PVA matrix. • The thermal stability of Cs/PVA film increased with increasing clay content. • Linear and nonlinear refractive indices enhanced as clay content increased. • Plasma frequency, resonance frequency, and electron lifetime were obtained. [ABSTRACT FROM AUTHOR]

In this study, a novel carboxymethyl cellulose (CMC)-based ternary nanocomposite films containing sodium montmorillonite (Na-MMT) (1, 3 and 5% wt) and titanium dioxide (TiO 2 ) (1, 3 and 5% wt) nanoparticles (NPs) were made via casting method. The results showed that addition of NPs decremented water vapor permeability of the films up to 39% and 50% by adding Na-MMT, and Na-MMT + TiO 2 , respectively, while moisture content, density and glass transition temperature incremented slightly. The nanoclays amplified resistance of the nanocomposites against tensile stress and Young's modulus (YM) of the films at the expense of elongation at break. A synergistic effect of NPs on moisture uptake reduction (≈ 40%) of films was observed. Nano-TiO 2 was strongly effective in UV-light blocking (The films containing 5% TiO 2 removed more than 99% of UV and more than 98% of visible lights). The interactions, crystallinity and morphology of the nanocomposites were investigated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). Development of hydrogen bonds between the hydroxyl groups of CMC and nanoparticles was indicated by FT-IR spectroscopy. Conforming to the XRD analysis, clay nanolayers organized an intercalated structure in the nanocomposites, whereas a limited agglomeration of TiO 2 nanoparticles led to increment of films crystallinity. SEM micrographs showed well-dispersed Na-MMT and TiO 2 NPs through the films surface especially at low concentrations. In conclusion, although the films loaded with nanoclays exhibited better properties than the control film, inclusion of TiO 2 more improved the functional characteristics of them and extended the potential as a biodegradable packaging. [ABSTRACT FROM AUTHOR]

Inhibiting the surface hydration of clay is the main task for the water-based drilling fluids used in the development of shale gas. Branching polyethyleneimine (BPEI) completely inhibits the clay surface hydration. However, the use of BPEI is limited by its high toxicity. In this paper, BPEI was modified by grafting with hydroxyethyl groups to reduce the toxicities of BPEI hydration inhibitors. The structures and properties of the modified BPEI were characterized by infrared spectroscopy, mass spectrometry, the luminescent bacteria method, isothermal adsorption, X-ray diffraction, thermogravimetric analysis, contact angle measurement, scanning electron microscopy, X-ray photoelectron spectroscopy and molecular simulations. The relative luminescence rate of the modified BPEI inhibitors increased from 14 % to 62 % with increases in the number of grafted hydroxyethyl groups. After hydrated sodium montmorillonite (Na–Mt) contacted the modified BPEI inhibitors, the basal spacings of the Na–Mt decreased from 1.90 nm to a minimum of 1.40 nm, and the DTG curve had only one low-temperature peak. Molecular simulations showed that the energy for adsorption of the inhibitor on the Mt surface increased with increases in the number of grafted hydroxyethyl groups. These results suggested a structure-activity relationship for inhibition and the biological toxicity of the modified BPEI inhibitor. That is, within the range of 20:1 to 5:1 for the molar ratios of amino and hydroxyl groups, increases in the number of grafted hydroxyethyl groups gradually decreased the biological toxicities of BPEI inhibitors, and the inhibition performance was gradually enhanced. BPEI-OH4 (amino:hydroxyl = 5:1) showed the best performance among the modified BPEI inhibitors. This provides an excellent inhibitor and a low-toxicity modification method, which will facilitate the development of environmentally friendly high-performance water-based drilling fluids. • The biotoxicity of BPEI was effectively reduced by grafting of hydroxyethyl groups. • The inhibition efficiency of BPEI was improved by grafting of the hydroxyethyl groups. • The adsorption capacity of BPEI was improved by grafting with different numbers of hydroxyethyl groups. • These results provide a way to decrease the toxicities of amino inhibitors without weakening the inhibition performance. [ABSTRACT FROM AUTHOR]

This work presents a novel way to produce a thermally stable nanoclay with an increased interlayer space, which are the essential requirements in fabricating clay-polymer nanocomposites. Sodium montmorillonite (Na-Mt) was functionalized through two separate, consecutive reaction systems. Functionalization with an aminosilane was first performed, in order to produce reactive groups at the silicate nanolayers. In the second step, amino acid monomers were employed for a further reaction with silane-modified nanoclay. X-ray diffraction results demonstrated an increased d 001 -value (24 Å) using 10 mmol γ-aminobutyric acid. The 001 reflection peak disappeared when 5 mmol ω-aminoundecanoic acid/g Mt was used as the second type of amino acid. Transmission electron microscopy images of modified Mt with 10 mmol ω-aminoundecanoic acid exhibited a well separated or exfoliated structure of nanolayers. Thermogravimetric measurements indicated a trend of increasing thermal stability of the modified nanoclays (350 °C to 400 °C) with increasing amounts of initial ω-aminoundecanoic acid. Based on these results, optimizing the modifiers and synthesis conditions can control the properties of modified nanoclay. Tensile modulus and strain at break of HDPE/2 mass% modified Mt showed 10% and 14% enhancements, respectively, due to the increased d 001 -value of the nanofiller, which results in greater filler-polymer interaction. [ABSTRACT FROM AUTHOR]

Montmorillonite (Mt) as a solid acid catalyst or support has been widely used in catalytic reactions. However, the existence and catalytic activities of its surface basic sites have rarely been revealed. Here, the surface and structure of Na-Mt are modulated by thermal treatment, providing both acidic and basic sites for the transesterification of glycerol with dimethyl carbonate (DMC) to glycerol carbonate (GLC). The experimental results showed that the thermally activated Na-Mt exhibited bifunctional catalytic properties in glycerol transesterification. The Na-Mt calcined at 400 °C had a basic site density of 1.38 mmol/g and led to a glycerol conversion of 96.8% and a GLC yield of 94.5%. Edge surfaces of Na-Mt provided MII (MIII) atoms as Lewis acidic sites for facilitating the generation of glyceroxide anions from activated glycerol and -M-OH groups as Brønsted and Lewis basic sites for enhancing the carbonyl activation of DMC. This work revealed the co-existence of acidic and basic sites over thermally activated Na-Mt for synergetic catalysis in the transesterification of glycerol to GLC, making the development of Mt-based materials as bifunctional catalysts for one-pot acid-base catalytic processes possible. • Coexisting acid and basic sites on sodium montmorillonite (Na-Mt) is revealed. • Reactive sites on edge surfaces of Na-Mt is altered with calcination temperature. • Synergetic effect of acid and basic sites results in high catalytic activity of Na-Mt. • Understanding on the structure-activity relationship of Na-Mt as bifunctional catalyst. • Bring insight into the surface and interface properties of Na-Mt. [ABSTRACT FROM AUTHOR]

Ionic liquids have attracted significant research interest due to their unique thermal stability. In this paper, the influence of a water-soluble ionic liquid on the rheological and filtration properties of water-based drilling fluids at high temperature is investigated. The drilling fluids are evaluated by means of rheological and filtration tests following the American Petroleum Institute (API) standards, submitted to an aging process or at high temperature. The experimental results show that the rheological behavior of water-based drilling fluids is improved and enhanced in the presence of low concentration of ionic liquid (as low as 0.05 mass%) at high temperatures (even up to 240 °C). Meanwhile, the high-temperature and high-pressure (HTHP) filtration volumes are reduced by as much as 52% compared with that of polymer water-based drilling fluids without ionic liquid. The study of the mechanism demonstrates that the water-soluble ionic liquid have an excellent capacity to improve the rheological and filtration properties of water-based drilling fluids at high temperatures due to the high thermal stability and cation exchange ability of the ILA. [ABSTRACT FROM AUTHOR]

Temperature affects significantly the rheological behavior of neat water Wyoming Na-bentonite dispersions. The results of a very systematic study are presented regarding rheological measurements of 7% mass concentration at different temperatures, ranging between 25 and 80 °C at atmospheric pressure. Higher temperature increased the shear stresses at low shear rates while the effect was much smaller at higher shear rates. The Herschel-Bulkley rheological model fitted extremely well all data. The yield stress increased linearly with temperature by almost three-fold, the flow consistency index decreased exponentially with temperature by almost five-fold and the flow behavior index increased by about 20%, tending towards the Newtonian value. At low shear rates (< 100 rpm corresponding to < 170 1/s Newtonian shear rates), which represent very well the shear rates experienced by drilling fluids in the critical annulus region, all rheograms appeared fairly linear and the Bingham plastic model fitted well all data. The Bingham yield stress, from the low shear rate data, increased linearly with temperature, while the plastic viscosity decreased with temperature, in a manner very similar to the decrease of water viscosity with temperature. The plastic viscosity and Bingham yield stress data, from the low shear rate range, can be fitted well by an Arrhenius-type equation, with the activation energy for the plastic viscosity very similar to the activation energy for water viscosity, while for the Bingham yield stress, the activation energy is equal but opposite in sign to that of the plastic viscosity. A hypothesis is stated for the the observed linear increase of the yield stress with temperature, in the temperature range studied. One should be concerned when non-standard preparation and measurement procedures are followed which makes extremely difficult to understand any differences observed when reporting rheological data of water bentonite dispersions. A standard methodology is proposed, complementary to API, which can give very consistent results. [ABSTRACT FROM AUTHOR]

In this work, a simple and reliable electrochemical method for the determination of cadmium using an antimony film modified sodium montmorillonite (NaMM) doped carbon paste electrode (Sb/NaMM-CPE) was described. Due to the strong cation exchange ability and adsorptive characteristics of NaMM and excellent electroanalytical performance of the antimony film, the new electrode significantly enhanced the sensitivity for detection of Cd(II) and exhibited superior performance in comparison with the bare carbon paste electrode, antimony film modified carbon paste electrode (Sb/CPE), and NaMM modified carbon paste electrode (NaMM-CPE). Some parameters such as the composition of the paste, pH of the measure solution, the Sb(III) concentration, deposition time, and deposition potential that influenced the response of cadmium were investigated and the procedure was optimized for cadmium determination. This electrode, combined with square-wave anodic stripping voltammetry, displayed excellent linear behavior in the examined concentration range of 4.0–150.0 μg L −1 Cd(II) ( R 2 = 0.998) with a detection limit of 0.25 μg L −1 . The Sb/NaMM-CPE was successfully applied to the determination of cadmium ion in tap water sample. [ABSTRACT FROM AUTHOR]

The electrochemical detection of ibuprofen has been studied on Palladium-Montmorillonite (Mt) modified carbon paste electrode using differential pulse voltammetry. The optimization of the modifier preparation and the instrumental parameters was investigated. The results indicate that ibuprofen oxidation was favored in the presence of Pd–PdO particles. The quantitative determination of ibuprofen was statistically analyzed and validated using HPLC method. The detection and quantification limits, specificity and precision were found to be acceptable. Finally, the developed method was successfully applied for ibuprofen determination in human blood samples. [ABSTRACT FROM AUTHOR]

Chitosan-montmorillonite composites can provide hydrophobicity and amino groups to enhance the performances of montmorillonite in wastewater treatment. In this paper, low molar mass chitosan (LC) and medium molar mass chitosan (MC) were selected to intercalate a sodium montmorillonite (Mt). The adsorption isotherm of LC and MC on the Mt and the pH dependency were measured. Thermo X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the chitosan-Mt composites. Results showed that with hydrochloric acid as the solvent of chitosans, increasing pH from 3 to 5.5 enhanced the adsorption of both LC and MC on the Mt, and when the equilibrium concentration of chitosans approached 300 mg/L at pH 5.5, the amount of adsorbed chitosan reached the highest level of 0.203 mg/mg for LC and 0.190 mg/mg for MC, respectively. When the Mt was saturated with the chitosan, the amino groups on the chitosan were bonded with the Mt through electrostatic interaction and there was monolayer of the chitosan in the interlayer space of Mt, which were confirmed by FTIR spectra and XRD patterns, respectively. [ABSTRACT FROM AUTHOR]

The sedimentation behavior of semi-dilute suspensions of sodium montmorillonite in the flocculation regime was studied as a function of ionic strength at pH 4.0 and 9.5 to elucidate the response of variation of macroscopic sedimentation behavior with microscopic particle association. The maximum velocity of the boundary between the supernatant and sediment and ultimate sediment height were chosen as indexes to evaluate the sedimentation behavior. Increment ratio of effective volume fraction of the particles (α) caused by the formation of flocs and hydrodynamic floc diameter were evaluated by Michaels and Bolger method on the basis of the Richardson–Zaki formula. The results clearly demonstrate that the maximum velocity of the boundary is strongly affected by both pH and salt concentration. The two observed patterns of variation of maximum sedimentation rate and ultimate sediment height can be clearly defined using 0.25–0.5 M NaCl as an inflection range. This range is consistent with the transition point at 0.3 M NaCl for the swelling behavior of sodium montmorillonite reported by Norrish. Below 0.25 M NaCl, the effect of pH on the sedimentation rate is remarkably enhanced compared with that at higher salt concentration. This effect is ascribed to the dominant appearance of edge–face (EF) particle interactions, which can be regarded as negligible at higher salt concentration. The reason for this is that the breakage of weak EF bonds is induced by the dominant appearance of face–face particle interactions at higher salt concentrations. That is, the decrease of repulsion strengthening the attraction between neighboring particles is responsible for EF bond breakage. The small influence of pH on ultimate sediment height at high salt concentration can be ascribed to the residual strong EF bonds. The Michaels and Bolger method can be used qualitatively at range of NaCl greater than 0.5 M. [ABSTRACT FROM AUTHOR]

Preparation of novel high substituted carboxymethyl starch-based microparticles containing sodium montmorillonite (MMT) by crosslinking with Al 3+ was described. For preparing nanocomposite granules carboxymethyl starch (CMS) from native potato starch as well as CMS from amylopectin has been used. The hydrophilic CMS/MMT composite systems were used for herbicide, i.e. isoproturon encapsulation (ca. 75% encapsulation efficiency). The herbicide release rate from CMS/MMT composites in water was significantly reduced when compared to commercial isoproturon: 95% released after ca. 700 h and ca. 24 h, respectively. Leaching in soil from composite systems was relatively slower than release in water. After a series of eight irrigations leached about 10% of isoproturon loaded. The CMS/MMT carriers could reduce the potential leaching of herbicide and beneficially reduce pollution of the environment. [ABSTRACT FROM AUTHOR]

In this experiment, we used a vacuum impregnation method to prepare shape stabilized PCM that contained sodium montmorillonite (Na-MMT) and Exfoliated graphite nanoplatelets (xGnP), to improve the thermal conductivity of PCMs, and prevent leakage of the liquid state of PCMs. Na-MMT has low cost and natural abundance, high adsorption and absorption capacities, and fire retardant heating rate. In the used materials, xGnP, usually produced from graphite intercalated compounds, are particles consisting of several layers of graphene sheets. As a result, we found that the FTIR adsorption spectra of paraffinic PCMs did not change, and there was no chemical interaction between paraffinic PCMs and xGnP/Na-MMT mixture. From the DSC analysis, xGnP made an impact on the thermal properties of the paraffinic PCMs/Na-MMT composites. The oxidation rate of paraffinic PCMs based composite with xGnP was greater than that of the composite without xGnP. FTIR, DSC, TGA and TCi were used to determine the characteristics of the paraffinic PCMs/Na-MMT composites. [ABSTRACT FROM AUTHOR]

In the present work, the effect of sodium montmorillonite (Na + Mt) on the resulting properties of semi-finished (crust) leather has been thoroughly studied. Na + Mt has been added during retanning process of tanned (wet-blue) leather in specific conditions. The morphological analysis by scanning electron microscopy has pointed out that Na + Mt particles are homogeneously distributed and finely dispersed within the leather structure. The presence of clay mineral has affected the thermal stability of leather in nitrogen and air (assessed by thermogravimetry), as well. According to the sixty second vertical flammability test results Na + Mt particles have significantly reduced the burning length of the semi-finished leather. A barrier mechanism of the Na + Mt during combustion process is proposed. Mechanical properties (namely, tensile and tear strength) have proven to be considerably improved by using 1 and 3 mass% of Na + Mt; these results have clearly indicated the reinforcing effect of clay mineral platelets that somehow physically interact with leather. [ABSTRACT FROM AUTHOR]

The role of non-ionic functionalization in modifying the physical and chemical properties of clay minerals and their potential as internal curing agents in cement composites have been remaining unclear. This work elucidates comprehensive insights into the functionalization of sodium montmorillonites (sMTs) with two non-ionic surfactants, t-octyl phenoxy poly ethoxyethanol (TX100) and polyethylene glycol ether (PEG10), and their influences on sMT properties. The results indicate that both TX100 and PEG10 are effectively intercalated into sMT resulting in increased interlayer spacing and hygroscopic swelling behavior. With the presence of functionalization, the water uptake capacity, ion exchange capacity, and dispersion of the sMT in both water and simulated cement pore solution are improved. With raised Al and Si dissolution, a significant improvement in pozzolanic reactivity of sMT is observed. Insights reported here pave a path for leveraging non-ionic functionalized sMT as a potential internal curing agent for cement hydration and concrete performance enhancement. • Sodium montmorillonite is functionalized with two non-ionic surfactants. • Effective intercalations of both TX100 and PEG10 in montmorillonite are obtained. • Interlayer spacing, vapor sorption and water uptake increase with surfactant dosage. • Swelling, Li release, Al/Si dissolution and dispersion in pore solution are raised. • Enhanced reaction heat and lime consumption indicate improved pozzolanicity. [ABSTRACT FROM AUTHOR]

Abstract: Sodium-montmorillonite (Na-MMT) nanoclay was modified with four different modifying agents, differing in alkyl chain lengths. The modified organoclay or modified Na-MMT was then compounded with natural rubber (NR) via melt mixing. The influence of alkyl chain length on the properties of organoclay and NR/organoclay nanocomposites was investigated. The longer alkyl chain lengths were more effective in intercalating and expanding the interlayer spacing of clay. Furthermore, the modification of organoclay accelerated the vulcanization reaction of NR, so that the rubber vulcanizates had an increased degree of crosslinking. The mechanical properties of NR were enhanced by the organoclay filling, and larger organoclays interlayer spacing increased the enhancement. This is due to increasing in the crosslinking density of nanocomposites and better dispersion of organoclay in the rubber matrix. A new technique, temperature scanning stress relaxation (TSSR), was used to characterize thermal-mechanical behavior of the composites. The initial stress correlated well with the mechanical properties of nanocomposites. In addition, stress relaxation was observed at the melting temperature of the agent used to modify the organoclay. The organoclays also enhanced the thermal stability, shifting the stress relaxation peaks to higher temperatures. [Copyright &y& Elsevier]

Abstract: Nanocomposites of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP) and sodium montmorillonite (Na+MMT) were prepared by solution mixing and then cast into films. X-ray diffraction analysis and images of transmission electron microscopy establish the formation of PVA/Na+MMT intercalated nanocomposite. Exfoliated and highly intercalated PVA/PVP/Na+MMT nanocomposite formed in the presence of PVP. Inclusion of PVP in PVA/Na+MMT matrix enhances the hydrogen bonding interactions between PVA and Na+MMT and thus increases the mechanical properties and thermal stability of PVA/PVP/Na+MMT nanocomposites compared to PVA/Na+MMT nanocomposite. The interactions between PVA, PVP and Na+MMT were established by the Fourier transform infrared spectroscopy. The moisture absorption tendency of both the PVA and PVA/PVP films reduced after the incorporation of Na+MMT at 75% constant relative humidity. Differential scanning calorimetry studies show that the presence of PVP and Na+MMT both are responsible for reducing the heat of fusion, and crystallinity of PVA. The flow behavior of the PVA, PVA/PVP and its nanocomposite solutions has been also studied. Water vapor permeability of PVA/PVP/Na+MMT composite films decreased in the presence of nanoclay due to increasing tortuous paths for diffusion. [Copyright &y& Elsevier]

Abstract: The adsorption of acid dye, namely, acid fuchsin (AF), onto sodium montmorillonite (Na+-Mt) from aqueous solutions was investigated. The adsorption process was very fast and attained equilibrium within 1h, which was an economically favorable requisite. The Freundlich and Langmuir adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were calculated. The experimental data fit well with Freundlich model rather than the Langmuir model. The equilibrium adsorption constant, K c, was determined and used to calculate the enthalpy and entropy of the adsorption process. The adsorption kinetics was followed up using a stopped-flow spectrophotometer under pseudo-first-order conditions. The influence of initial dye concentrations, amount of sodium montmorillonite, and temperature on the rate of adsorption were studied. The activation energy of adsorption was calculated and indicated a chemical adsorption process. The enthalpy of adsorption confirmed an exothermic process. A proper mechanism for adsorption supported by X-ray and atomic absorption data was proposed. [Copyright &y& Elsevier]

Highlights: [•] Modular β-cyclodextrin water-soluble copolymers were prepared for EOR. [•] The copolymers were characterized by IR, 1H NMR SEM, XRD, core flood test, etc. [•] The copolymers showed excellent shear, temperature resistance and salt tolerance. [•] The results of EOR and MMT crystalline interspace were remarkable. [ABSTRACT FROM AUTHOR]

Abstract: Titanium tetrafluoride (TiF4) is an effective but instable caries preventive agent. As the stability problems could be minimized through the use of drug carriers this study aimed to prepare and characterize a new TiF4 nanoinclusion complex and to evaluate its potential in inhibiting enamel demineralization under pH cycling conditions. The TiF4 nanosystems were prepared using β-cyclodextrin (βCD) and sodium montmorillonite (MMTNa). Bovine enamel blocks (n =48) with known surface microhardness (SMH), were randomly assigned to 4 groups (n =12) and submitted to one of the following treatments: distilled deionized water (as negative control) and solutions containing 1% βCD, 1% TiF4 and TiF4:βCD. The solutions were blinded applied once on the blocks with a microbrush® on the surface for 1min before pH-cycling. After that, samples were reavaluated by SMH, %SMH loss, cross-sectional microhardness (CSMH), scanning electron microscope (SEM) and energy dispersive spectrometry (EDX). The inclusion complex of TiF4:βCD offered better protection against demineralization in the subsurface. The SEM analysis showed that TiF4 and TiF4:βCD samples presented the most intact enamel than the control. The EDX analysis identified titanium in TiF4 and TiF4:βCD groups. TiF4:βCD has higher potential on inhibiting demineralization in the inner enamel. TiF4:βCD is a new alternative to TiF4 stabilization in order to reduce enamel subsurface demineralization. [Copyright &y& Elsevier]

Abstract: Clay materials are well suited for heavy metal adsorption in view of their excellent surface area and cation exchange capacity. In this paper, we report the detailed study on the adsorption of hexavalent chromium using dodecylamine intercalated sodium montmorillonite as a potential adsorbent. The adsorption involves primarily the electrostatic interaction of hydrogentetraoxochromate(VI) anion with the protonated dodecylamine and the surface hydroxyl groups of the clay material. The pseudo second order kinetic model fits the experimental data and an adsorption capacity of 23.69mgg−1 was obtained from the Langmuir isotherm model. The exothermically favorable spontaneous adsorption process and the decrease in entropy explain the thermodynamics of the adsorption. The adsorbent could be regenerated using NaOH and column adsorption studies provide a sample break through volume of 300mL on a laboratory scale. The adsorbent could be utilized for the successful removal of chromium from tannery wastewater. [Copyright &y& Elsevier]

Abstract: For high performance waterborne coatings usually polymer latexes with low emulsifier content are more preferred. Although polymer/clay nanocomposites offer improved properties, it is difficult to produce clay based nanocomposite latexes containing low emulsifier due to the stabilization problems especially caused by organoclays. Present study deals with the preparation of a tBA/BA/MAA ternary copolymer/clay nanocomposite containing 3wt.% sodium montmorillonite (Na+-MMT) via seeded emulsion polymerization. Experimentally it was observed that even the usage of hydrophilic clay caused stabilization problem and a certain amount of emulsifier (>1wt.%) was necessary to obtain stable latexes. In addition, the usage of a low molecular weight water soluble polymer as steric barrier was found to increase the stability of system. Obtained nanocomposite latex showed fine particle size diameter (127nm) and very narrow size distribution (PDI=0.06). The WAXD and TEM investigations indicated that a mostly exfoliated nanocomposite was obtained. Thermal analyses (DSC, DMTA and TGA) showed that there was no change at T g of the copolymer while very high improvement was obtained for elastic modulus and a slight increase in thermal stability. According to the rheological measurements, the nanocomposite latex showed a higher low shear viscosity, a stronger shear thinning behavior and an improved physical stability in comparison to the reference latex. [Copyright &y& Elsevier]

Abstract: Polyethersulfone (PES)-based mixed matrix membranes (MMMs) with the incorporation of inorganic fillers of different shapes (lamellar Na-montmorillonite (MMT) clays and spherical TiO2 nanoparticles) were prepared in this study, and the resulting MMMs were characterized by TGA, DSC, XRD, SEM, and TEM. It was found that inorganic filler agglomeration became more serious at higher-filler-content MMMs. In the case of PES/MMT MMMs, both the CO2 and CH4 permeabilities increased significantly with the increasing filler content and consequently the gas selectivity was greatly reduced. At high MMT loadings (⩾10 wt.%), Knudsen diffusion became the predominant gas transport mechanism. A different trend was achieved in the case of PES/TiO2 MMMs. The CO2/CH4 selectivity increased from 24.5 (pure PES membrane) to a maximum value of 38.5 at 4 wt.% TiO2 MMM and then decreased with a further increase in TiO2 content (e.g. 17.3 for 20 wt.%). The formation of interface voids and membrane defects in MMMs contributed to the high gas permeabilities and low gas selectivity. [Copyright &y& Elsevier]

Abstract: A simple yet accurate model describing the viscosity of dilute suspensions of sodium montmorillonite in dilute homoionic solutions is presented. Taking the clay particle and the surrounding clouds of ions as a whole as an uncharged but soft, coin-like particle, the Huggins’ equation for a suspension of uncharged particles is extended in the model to account for not only the primary and the secondary electroviscous effects, but also the multi-particle interaction. The agreements between the predicted and measured results are excellent. The Huggins’ coefficient obtained compares favorably with available data, while the intrinsic viscosity reduces to the Simha’s equation in the large limit of ionic strength, suggesting that the model is robust. [Copyright &y& Elsevier]

Abstract: The kinetics of the emulsion copolymerization of methyl methacrylate/butyl acrylate (MMA/BA=50/50) in the presence of sodium montmorillonite (Na-MMT) was investigated. Sodium laurylsulfate was used as surfactant at different concentrations and potassium persulfate as initiator. Two series of experiments were carried out at 30% and 10% solids content and varying the amount of surfactant and sodium montmorillonite. The effect of surfactant and sodium montmorillonite content on the stability of the final latices was assessed. The effect on particle nucleation, polymerization kinetics and molar mass distribution was also discussed, and compared with the predictions of the Smith–Ewart theory. [ABSTRACT FROM AUTHOR]

Abstract: A two-step process has been developed to disperse sodium montmorillonite(Na+-MMT) in organic liquid N,N-dimethylformamide(DMF) and was applied in preparation of poly(ε-caprolactone)(PCL) nanocomposites. The dispersion of Na+-MMT particles in DMF was evaluated by laser diffraction and the dispersion of Na+-MMT particles in composites was investigated by transmission electron microscopy(TEM) and X-ray diffraction(XRD). TEM result indicated that the average lateral dimension of Na+-MMT particles in composites was approximately 300 nm and the thickness was less than 20 nm. The impact of Na+-MMT on the crystallization behavior and thermal resistance of PCL were determined by differential scanning calorimetry(DSC) and thermal gravimetric analysis(TGA), respectively. The impact of Na+-MMT on biodegradability of PCL was also studied. [Copyright &y& Elsevier]

Abstract: The adsorption of rhodamine B dye was carried out using sodium montmorillonite clay. The effect of parameters such as pH, adsorbent dosage and initial dye concentration was studied. The Langmuir and Freundlich isotherm models were applied and the Langmuir model was found to best fit the equilibrium isotherm data. Langmuir adsorption capacity was found to be 42.19mg/g. Kinetic data followed pseudo-second-order kinetics. Maximum color removal was observed at pH 7.0. The ΔG° value was found to be negative, the adsorption process was feasible. The results indicate that sodium montmorillonite clay can be used for the removal of basic dyes from aqueous solutions. [Copyright &y& Elsevier]

Abstract: We fabricated hybrid Langmuir–Blodgett (LB) films of a smectite clay and chiral tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate which has no long alkyl chain. Characteristics of the films were compared with those of the films consisting of a racemic mixture of the same complexes by means of pressure–area (π–A) isotherm measurements, linear and nonlinear optical spectroscopies and atomic force microscopy (AFM). Similar to the case with the films of the racemic metal complex, the density of the chiral metal complexes adsorbed onto the surface of the clay sheet was found to be controlled by changing the film fabrication conditions. The optical second-harmonic generation circular-dichroism (SHG-CD) response from a chiral film indicated the existence of a chiral molecular array on the surface of the clay sheets. [Copyright &y& Elsevier]

Abstract: This work is devoted to study the sedimentation behavior in concentrated suspensions of magnetite-covered clay particles. These core–shell particles were prepared by adhesion of synthetic magnetite nanoparticles on sodium montmorillonite platelets in aqueous solution at pH 3 and 2×10−3 mol/L NaNO3 ionic strength. A new experimental device, suitable for measuring the time evolution of the local volume fraction in concentrated opaque suspensions of magnetizable particles, is described. The experimental method is based on the variations of the resonant frequency of an oscillating parallel LC circuit in which the coil surrounds a test tube filled with the magnetic suspensions. The sedimentation rate in suspensions with different volume fraction and variable magnetite to clay volume fraction ratio was measured. The results are analyzed considering the effect of both the total energy of interaction between the clay–magnetite (core–shell) particles and the total solid volume fraction of the suspensions. [Copyright &y& Elsevier]

Abstract: Poly(vinyl alcohol)-based mixed matrix membranes loaded with 5 and 10wt.% of sodium montmorillonite (Na+MMT) clay particles, i.e. (PVA/Na+MMT-5 and PVA/Na+MMT-10), were fabricated by solvent casting method. The uncrosslinked membranes were used in pervaporation (PV) dehydration of aqueous solutions of isopropanol and 1,4-dioxane at 30°C. Membrane morphology was characterized by scanning electron microscopy. Differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical thermal analysis were used to understand thermal properties. Universal testing machine was used to study mechanical strength properties. Separation factor to water has increased from 1116 to 2241 for PVA/Na+MMT-5 and PVA/Na+MMT-10 mixed matrix membranes when tested for 10wt.% water-containing isopropanol feed, but the corresponding flux values of 0.051 and 0.075kg/m2 h were somewhat lower than those observed for pristine PVA membrane. On the other hand, for water+1,4-dioxane feed mixtures, separation factors were quite lower and ranged from 216 to 369 with the corresponding flux values of 0.076 and 0.093kg/m2 h, respectively, for PVA/Na+MMT-5 and PVA/Na+MMT-10 membranes at 10wt.% water in the feed. Membranes of this study could extract up to 99.20 and 99.60wt.% water on the permeate side from water–isopropanol mixture, while from water–1,4-dioxane mixture, only 96.0 and 97.62wt.% of water were removed for 10wt.% water-containing feed. The membranes were further tested for PV at 40, 50 and 60°C for 10wt.% of water-containing feeds of aqueous isopropanol and 1,4-dioxane solutions to confirm their stability at higher temperatures. Plots of ln J p versus 1/T are linear in the studied range of 30–60°C for both the feed mixtures, indicating that flux follows an Arrhenius trend. PV results are discussed in terms of water flux, separation factor, permeation separation index, enrichment factor and activation energy of permeation. Sorption and PV experiments were carried out for the thermally crosslinked and glutaraldehyde crosslinked PVA/Na+MMT mixed matrix membranes for 10wt.% water-containing feed mixtures at 30°C. A small increase in separation factor with a slight sacrifice in flux was observed without showing any great difference as compared to uncrosslinked mixed matrix membranes. The hydrophilic nature of Na+MMT clay and the formation of PVA/Na+MMT mixed matrix membranes are responsible to offer such increased separation to water over the organic components of the feed mixtures. [Copyright &y& Elsevier]

Abstract: Novel hybrid composite membranes have been prepared by incorporating 5 and 10wt.% of sodium montmorillonite (Na+MMT) clay particles into sodium alginate (NaAlg) and crosslinked with glutaraldehyde. Pervaporation (PV) separation performance of the hybrid composite membranes has been investigated for dehydration of isopropanol, 1,4-dioxane and tetrahydrofuran (THF) from their aqueous solutions at 30°C. The effect of Na+MMT in sodium alginate membrane has been investigated in the pervaporation dehydration. It is found that Na+MMT particles can be intercalated in the aqueous polymer solution. The driving force for Na+MMT adsorption is entropic, which involves at least partial replacement of water of hydration associated with exchangeable cations in the clay galleries. The results of PV experiments demonstrated that addition of Na+MMT clay particles would help to increase the selectivity to water over that of pristine NaAlg membrane by pushing its limit to infinity giving a moderate flux. Permeation fluxes of the hybrid composite membranes were lower than those observed for plain NaAlg membrane. [Copyright &y& Elsevier]

Abstract: We fabricated hybrid Langmuir–Blodgett (LB) films of smectite clays and a metal complex (tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate) which has no long alkyl chain. Characteristics of films fabricated on an aqueous suspension of synthetic saponite were compared with films fabricated on an aqueous suspension of natural sodium montmorillonite by means of nonlinear and linear optical spectroscopy, pressure–area (π–A) isotherm measurement and atomic force microscopy (AFM). AFM studies revealed that the homogeneity of a hybrid LB film fabricated on an aqueous suspension of synthetic saponite is considerably higher than that of a film fabricated on an aqueous suspension of montmorillonite. [Copyright &y& Elsevier]

Abstract: A novel amperometric sensor for the determination of hydrogen peroxide was prepared based on the enhanced oxidation of H2O2 at a glassy carbon electrode modified with colloidal MnO2–Na-montmorillonite (nano-MnO2/Na-Mont/GCE). The montmorillonite has been devised to support and dispense the MnO2 nanoparticles. Scanning electron microscopy images (SEM) showed that the MnO2 nanoparticles were homogeneously dispersed in the colloidal Na-montmorillonite. This colloidal dispersion was dried to form a uniform film when added to the surface of GCE. The voltammetric results showed that MnO2 nanoparticles could effectively catalyze the oxidation of H2O2. The dependence of the response current on H2O2 concentration was explored under optimal conditions, and an excellent linear relationship was obtained in the range from 5×10−7 to 7.5×10−3 M with a minimum detectable concentration of 1.5×10− 7 M. This sensor has been applied to measure trace concentration of hydrogen peroxide in samples of hair dye. [Copyright &y& Elsevier]

Abstract: As a part of the safety assessment of the geological disposal of high-level radioactive waste, the effects of dry density and exchangeable cations on the diffusion process of Na+ ions in compacted bentonite were studied from the viewpoint of the activation energy for diffusion. The apparent self-diffusion coefficients of Na+ ions in compacted Na-montmorillonite and in a Na- and Ca-montmorillonite mixture were determined by one-dimensional, non-steady diffusion experiments at different temperatures and dry densities. A unique change in activation energy as a function of dry density was found for the Na+ ions in compacted Na-montmorillonite. The activation energy suddenly decreased from 18.1 to 14.1 kJ mol−1 as the dry density increased from 0.9 to 1.0 Mg m−3, whereas it increased to 24.7 kJ mol−1 as the dry density increased to 1.8 Mg m−3. Examination of the effect of exchangeable cations on the activation energies determined that the activation energies were almost constant, approximately 25 kJ mol−1, for the montmorillonite specimens at a dry density of 1.8 Mg m−3. However, three different activation energy values were obtained at a dry density of 1.0 Mg m−3. These findings cannot be explained by the conventional diffusion model (the pore water diffusion model), which suggests that the predominant diffusion process alternates among pore water diffusion, interlayer diffusion, and external surface diffusion. [Copyright &y& Elsevier]

A series of novel low molecular weight alkyldiammoniums with different alkyl chain lengths were synthesized. Alkyldiammoniums as intercalation inhibitor with an arrangement of flat monolayer intercalates into the interlamination of sodium montmorillonite (Na-Mt), replaces the exchangeable cations, blocks the adsorption of water molecules or replaces water molecules adsorbed, tauts adjacent crystal layer of Na-Mt, minimizes the d 001 values of Na-Mt and thus, inhibit the hydration of Na-Mt. • A series of alkyl diammonium with different alkyl chain lengths were synthesized. • Alkyl diammonium as intercalation inhibitor can inhibit the swelling of Na-Mt. • The alky chain length has a great influence on the arrangement of the inhibitor. • Molecular dynamics simulations verifies the experimental results. Effective inhibition of mud shale hydration and swelling is the major challenge for water-based drilling fluids (WBDFs). In this paper, a series of novel low molecular weight alkyl diammoniums with different alkyl chain lengths was synthesized and evaluated as montmorillonite swelling inhibitor. The inhibition behavior of alkyl diammonium was studied by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), cation exchange capacity (CEC), and molecular dynamics simulation. The XRD results illustrated that the inhibitors (Gs-9, Gs-10, Gs-11, Gs-12, Gs-13 and Gs-14) rapidly lowered the basal spacing (d 001 value) of hydrated sodium montmorillonite (Na-Mt) from 1.92 nm to 1.41 nm, which indicates that a flat monolayer of inhibitors was inserted into the interlamination of Na-Mt. The XPS and CEC results showed that the alkyl diammonium displaced exchangeable cations in the interlamination of Na-Mt. The SEM results showed that the alkyl diammonium effectively improved the surface structure and curled edges of hydrated Na-Mt. The simulated results showed that the quaternary ammonium functional groups were fixed firmly on the six- oxygen rings of Na-Mt. The adsorption energy of alkyl diammonium increased with the increase in alkyl chain length. Therefore, alkyl diammonium with long alkyl chain can decrease the amount of inhibitor adsorbed on Na-Mt, thus reducing the dosage of inhibitor used in the WBDFs. This is conducive to reducing drilling costs. Therefore, this research on the inhibition behavior of alkyl diammonium with different hydrophobic chain lengths has important reference value for the development of WBDFs and suitable inhibitors for them. [ABSTRACT FROM AUTHOR]

With overwhelming progress in the field of electronic technology, self-healable hydrogel electrolyte-based supercapacitors are of significant interest as a power source in wearable energy storage devices. Self-healable hydrogel with unique three-dimensional porous microstructure, unprecedented self-healing, high capacitive energy density, low power density has been synthesized by in situ polymerization of acrylamide in the presence of exfoliated sodium montmorillonite (Na-MMT) clay as non-covalent cross-linker. Furthermore, addition of lithium trifluoromethanesulfonate (LiTF) salt converted the hydrogel into electrolyte for use in supercapacitor. Hydrogel electrolytes were prepared containing 10, 20, 30, and 40 wt% salt (AAM1, AAM2, AAM3, and AAM4), respectively. Acrylamide, clay and salt interactions were explored by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and energy dispersive x-ray analysis (EDX). X-ray diffraction (XRD) analysis reveals amorphous nature whereas FTIR and transference number measurements prove the complexation and presence of ionic species in the hydrogel electrolytes. Ionic conductivity and transport studies for hydrogel electrolyte containing 30 wt% of LiTF showed maximum ionic conductivity of 9.34 × 10−3 S/cm and number density of 70.7 × 10 20 cm−3, diffusion coefficient of 2.16 × 10 −9 cm2/s, ionic mobility of 0.854 × 10−7 cm2/V.s among all the synthesized hydrogel electrolytes. The electrochemical performance of the fabricated device disclosed the maximum significant specific capacitance of 102 F/g at 3 mV/s and 157 F/g at 50 mA/g along with power density of 50 W/kg and energy density of 21.59 W h/Kg, respectively for hydrogel electrolyte (AAM3) containing 30 wt% of the LiTF. Self-healing properties of hydrogel electrolyte have been confirmed by its use in supercapacitor where it retained its self-healing properties. The self-healable supercapacitor was used to light up 2 V light emitting diode (LED). Hence, investigations suggest the potential application of the hydrogel electrolytes with 30 wt% LiTF in the supercapacitors. Image 1 • Synthesis of self-healable and flexible poly (acrylamide) hydrogel electrolytes. • Deconvolution of FTIR spectra to find out free ions and contact ions. • Crystallite size and % crystallinity measurements through XRD. • Fabrication of self-healable supercapacitor device to power up light emitting diode. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the effect of the addition of sodium montmorillonite (Na+Mt) on the flexural strength, flexural modulus, degree of conversion, steady state shear viscosity and complex viscosity of the Bis-GMA (2,2-bis-[4-(methacryloxypropoxy)-phenyl] propane)/TEGDMA (ethane-1,2-diylbis(oxy)) bis (ethane-2,1-diyl) bis(2-methylacrylate) resin. Two types of clay polymer nanocomposites (CPN) were prepared, the first one by using sodium montmorillonite as received (Na+Mt) and the second one by adding sodium montmorillonite previously dispersed in water (Na+Mt/H 2 O). Sodium montmorillonite was added at different contents: 0.1, 0.2, 0.3, 0.4 parts per hundred of resin (phr) to Bis-GMA/TEGDMA resin for each type of CPN. A Bis-GMA/TEGDMA resin, without sodium montmorillonite, was used as control. Two-way ANOVA and Tukey's test were applied for statistical analysis. Comparisons were performed using a significance level of α = 0.05. Statistical analysis revealed that the addition of sodium montmorillonite as received or dispersed in water, had no effect on flexural strength (p =.886), flexural modulus (p =.809) and degree of conversion of resin (p =.742). Nevertheless, the content of sodium montmorillonite significantly influenced the flexural strength (p =.004) and flexural modulus (p <.001) of the two types of CPN. Flexural strength was increased when 0.1, 0.2 and 0.3 phr of Na+Mt or Na+Mt/H 2 O was used. Flexural modulus increased when 0.3 and 0.4 phr of Na+Mt or Na+Mt/H 2 O were added to resin. X-ray diffraction measurements showed that polymer chains were successfully introduced in the interlayer space of the clay mineral producing polymer intercalation. Scanning electron microscopy showed a rough surface for both CPN groups evaluated which evidenced electrostatic interactions between the clay mineral and the polymer matrix. Rheological behavior evidenced the physical interaction between clay mineral layers and polymer matrix. The incorporation up to 0.3 phr of sodium montmorillonite improved the mechanical and chemical properties of the Bis-GMA/TEGDMA resin. • Low content of sodium montmorillonite improves flexural strength of dental resin. • Intercalated clay mineral layers do not interfere in light-cured of dental resin. • Low content of water promotes the intercalation of sodium montmorillonite. [ABSTRACT FROM AUTHOR]

A model for explaining the effect of ionic strength on the yield stress and thixotropic behaviour of sodium montmorillonite or NaMt (SWy-2) gel was presented. NaMt gels displayed thixotropic behaviour at low to 0.1 M KCl concentration. This behaviour is reflected by an increasing yield stress with rest time after preshearing. The increasing yield stress measured the strengthing of the gel structure as it recovered at rest. The microstructure was formed by highly flexible nanosized platelets interacting both attractively via heterogeneous charge attraction in the edge-face and overlapping edge-edge configurations, and repulsively between the faces via electric double layer (EDL) force. This EDL force opened up the microstructure and was responsible for both the strength and thixotropic behaviour of the gel. The increasing gel strength with ionic strength up to 0.1 M KCl was a result of the weakening of the EDL force between the faces (interacting at an angle) particularly at the platelet bond forming the network junctions. The heterogeneous charge attraction forming the bond effectively increased in strength. In addition, weak platelet bonds were also able to form. The EDL force governs the microstructure development and this process takes a long time for every platelet to experience a minimum net force. The Leong model described the ageing or thixotropic behaviour quite well. At higher KCl concentrations, the van der Waals attractive force dominated the platelet-platelet interactions. These suspensions displayed time independent behaviour and was found to belong to the flocculated phase state. • EDL repulsive force governs the 3-D gel structure development • EDL force is responsible for the time-dependent behaviour. • Gel formed by vdW forces at high ionic strength is time independent. • Time-dependent gel corresponded to the flocculated phase state. [ABSTRACT FROM AUTHOR]

Hydrogel materials are receiving increasing research interest due to their intriguing structures that consist of a crosslinked network of polymer chains with interstitial spaces filled with solvent water. This feature endows the materials with the characteristics of being both wet and soft, making them ideal candidates for electrolyte materials for flexible energy storage devices, such as supercapacitors that are under intensive studies nowadays. In this study, hybrid poly (N, N-dimethylacrylamide) (PDMA) hydrogels were prepared through free radical mechanism. Ammonium persulfate was used as a free radical initiator while sodium montmorillonite was used as a crosslinker. Magnesium trifluoromethanesulfonate (MgTf 2) and cobalt oxide (Co 3 O 4) nanoparticles were added to provide the conduction pathway. The synthesized hydrogels were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). The presence of Co 3 O 4 nanoparticles in the hybrid hydrogel was confirmed using energy dispersive X-ray spectroscopy (EDX). The ionic conductivity study was performed using electrochemical impedance spectroscopy (EIS). The ionic conductivity study revealed that hydrogel containing MgTf 2 and Co 3 O 4 nanoparticles (DMA3) has the highest ambient ionic conductivity (9.4 × 10−3 S cm−1, respectively), dielectric permittivity, and lowest activation energy (0.094 eV). Transference number of hydrogel electrolyte was measured which described the movement of ions due to the presence of salt ions and nanoparticles. Furthermore, electrochemical performance of the synthesized hydrogels in electric double layer capacitor (EDLC) was examined using activated carbon electrode. The electrochemical studies such as cyclic voltammetry (CV) and galvanic charge-discharge (GCD) revealed that hydrogel containing MgTf 2 and Co 3 O 4 nanoparticles (DMA3) hydrogel showed maximum specific capacitance of 26.1 F g−1 at 3 mV s−1 and 29.48 F g−1 at 30 mA g−1, respectively. Additionally, it was able to withstand 97.4% of capacitance from its initial capacitance value over 8000 cycles at a current density of 200 mA g−1. The fabricated device revealed the successful light up of light emitting diode (LED). Hence, it can be said that the synthesized hydrogel electrolyte has significant potential for smart, light weight, and flexible electronic devices. [ABSTRACT FROM AUTHOR]