Sodium Montmorillonite Research Articles

Novel Poly(Vinylidene Fluoride)/Montmorillonite Polymer Inclusion Membrane: Application to Cr(VI) Extraction from Polluted Water.

Novel hybrid polymer inclusion membranes (PIMs) based on poly(vinylidene fluoride) (PVDF) (polymer matrix) and Aliquat 336 (ion carrier) and containing native sodium (Cloisite Na+ (CNa)) and organo-modified (Cloisite 30B (C30B)) Montmorillonites were elaborated and tested for the removal of toxic Cr(VI) ions from the aqueous solution. The influence of the nanoclay incorporation on the physicochemical properties of PVDF-based PIMs was studied and the resulting membrane transport properties of the Cr(VI) ions were investigated in detail. The water contact angle measurements reveal that the incorporation of the CNa nanofiller affects the membrane wettability as less hydrophilic surface is obtained in this case—~47° in the presence of CNa as compared with ~15° for PIMs with C30B. The membrane rigidity is found to be dependent on the type and size of the used Montmorillonite. The increase of Young’s modulus is higher when CNa is incorporated in comparison with C30B. The stiffness of the PIM is strongly increased with CNa amount (four times higher with 30 wt %) which is not the case for C30B (only 1.5 times). Higher Cr(VI) permeation flux is obtained for PIMs containing CNa (~2.7 µmol/(m2·s)) owing to their porous structure as compared with membranes loaded with C30B and those without filler (~2 µmol/(m2·s) in both cases). The PIM with 20 wt % of native sodium Montmorillonite revealed satisfactory stability during five cycles of the Cr(VI) transport due to the high membrane rigidity and hydrophobicity. Much lower macromolecular chain mobility in this case allows limiting the carrier loss, thus increasing the membrane stability. On the contrary, a deterioration of the transport performance is recorded for the membrane filled with C30B and that without filler. The obtained results showed the possibility to extend the PIM lifetime through the incorporation of nanoparticles that diminish the carrier loss (Aliquat 336) from the membrane into the aqueous phase by limiting its mobility within the membrane by tortuosity effect and membrane stiffening without losing its permselective properties.

Application of Edible Montmorillonite Clays for the Adsorption and Detoxification of Microcystin.

Exposure to microcystins (MCs) in humans and animals commonly occurs through the consumption of drinking water and food contaminated with cyanobacteria. Although studies have focused on developing water filtration treatments for MCs using activated carbon, dietary sorbents to reduce the bioavailability of MCs from the stomach and intestines have not been reported. To address this need, edible calcium and sodium montmorillonite clays were characterized for their ability to bind MC containing leucine and arginine (MC-LR) under conditions simulating the gastrointestinal tract and compared with a medical-grade activated carbon. Results of in vitro adsorption isotherms and thermodynamics showed that binding plots for MC-LR on montmorillonites fit the Langmuir model with high binding capacity, affinity, Gibbs free energy, and enthalpy. The in silico results from molecular modeling predicted that the major binding mechanisms involved electrostatics and hydrogen bonds, and that interlayers were important binding sites. The safety and detoxification efficacy of the sorbents against MC-LR were validated in a battery of living organisms, including Hydra vulgaris, Lemna minor, and Caenorhabditis elegans. The inclusion of 0.05% and 0.1% montmorillonite clays in hydra media significantly reduced MC-LR toxicity and protected hydra by 60-80%, whereas only slight protection was shown with the heat-collapsed clay. In the Lemna minor assay, montmorillonites significantly enhanced the growth of lemna, as supported by the increase in frond number, surface area, chlorophyll content, and growth rate, as well as the decrease in inhibition rate. Similar results were shown in the C. elegans assay, where montmorillonite clays reduced MC-LR effects on body length and brood size. All 3 bioassays confirmed dose-dependent protection from MC-LR, validated the in vitro and in silico findings, and suggested that edible montmorillonites are safe and efficacious binders for MC-LR. Moreover, their inclusion in diets during algal blooming seasons could protect vulnerable populations of humans and animals.

Agar/maltodextrin/poly(vinyl alcohol) walled montmorillonite composites for removal of methylene blue from aqueous solutions

Nowadays, the impact of textile pollutants such as methylene blue on aquatic systems is intensively serious over the world. There is a growing interest in the mitigation of these textile compounds using recyclable, high-efficiency, and biodegradable materials. Herein, we report a facile casting method for preparing agar/maltodextrin/poly(vinyl alcohol) walled montmorillonite (AMP–MMT) composites. Specifically, sodium montmorillonite clay was incorporated into hydrogel membranes with the loading rates of 0–30% (w v–1). Composite membranes were physicochemically characterized with physicochemical techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and zeta potential measurement. Other measurements of contact angle, moisture, and swelling degree were also conducted. Moreover, the effect of operating parameters such as montmorillonite loading, solution pH, contact time, concentration, and temperature on dye adsorption was explored. Plausible mechanisms of cation exchange, H–bonds, and n–π interactions might shed light on the adsorption of methylene blue on AMP–MMT composite. Nonlinear kinetic and isotherms were used to gain insight into adsorption nature. Composite membrane in our study exhibited high uptake capacity (71.51 mg g–1), good recyclability (at least five cycles), and easy desorption with green eluent of mixed water and ethanol. This work is expected to encourage the use of recyclable, eco-friendly, and biodegradable hydrogel membranes in the water purification.

Fabrication of aqueous solid-state symmetric supercapacitors based on self-healable poly (acrylamide)/PEDOT:PSS composite hydrogel electrolytes

The composite hydrogel electrolytes developed from conducting polymers own superb/excellent conductive, self-healing, and mechanical properties. However, it is still challenging to exploit them in energy storage devices. To address this issue, novel poly(acrylamide)/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) composite hydrogel electrolytes were developed through free radical polymerization in which sodium montmorillonite clay was added as a physical crosslinker. The different amounts of PEDOT:PSS were added to the composite hydrogel electrolytes. The structure of the synthesized composite hydrogel electrolytes was investigated by X-ray diffraction (XRD) analysis. The surface morphology of the composite hydrogel electrolyte was examined with the field emission scanning electron microscopy (FESEM) and elemental composition was determined using energy-dispersive X-ray spectroscopy (EDX). The ionic conductivity was measured at ambient temperature. Among the synthesized electrolytes, PEDOTAAM34 achieved the highest ionic conductivity of 13.7 × 10−3 S/cm at room temperature. Furthermore, electrochemical studies were performed by sandwiching the composite hydrogel electrolytes between symmetric carbon-coated graphite electrodes. The fabricated AC/PEDOTAAM34/AC based symmetric supercapacitor attained the highest specific capacitance of 327 F/g at 3 mV/s and 385.4 F/g (energy density of 53.57 Wh/kg at a power density of 100.08 W/kg) at 100 mA/g current density. The self-healable characteristics of symmetric supercapacitors were confirmed by powering up a light-emitting diode (LED).

The synthesis and characterization of phenolic resin with a high content of dimethylene ether bridges

Phenolic resins were synthesized using sodium montmorillonite (MMT) as a catalyst at a concentration of 3%, 5%, and 10%, the reaction time was 24 and 48 h, respectively. The phenolic resin yield was up to 69%. The chemical structure of the resins was determined by NMR, the thermal properties were determined by DSC and TGA, and molar masses were determined by SEC. The resins could not be easily classified as resol or novolac because the most common type of bonding between the aromatic rings was dimethylene ether (DME) bridges. Due to near neutral pH (6.7–7.1), some methylol groups were also present in the structure. Increasing the MMT concentration increased the molar mass of the resin; however, no influence of reaction time was observed. Increased MMT concentration, as well as longer reaction time, decreased the glass transition temperatures, which were very low, in the range of 8–24 °C. Increased content of DME increased the thermal stability of the resins.

Zirconium oxide intercalated sodium montmorillonite scaffold as an effective adsorbent for the elimination of phosphate and hexavalent chromium ions

The presence of oxyanions such as hexavalent chromium (Cr(VI)) and phosphate in water resources posing significant threat to both environment and human beings. Therefore, the present investigation focused on the elimination of phosphate and Cr(VI) anions from water by employing zirconium oxide intercalated sodium montmorillonite (ZrO2-NaMMT@700) composite as an adsorbent. The prepared ZrO2-NaMMT@700 composite was characterized using Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analyzer. The surface characterization results confirmed the successful intercalation of ZrO2 nanoparticles into NaMMT. The ZrO2-NaMMT@700 composite showed better and rapid removal for phosphate and Cr(VI) anions with the maximum adsorption capacity of 64.57 and 52.46 mg/g, respectively. The adsorption studies suggested that removal of phosphate and Cr(VI) was mainly driven by the electrostatic attraction and electrostatic attraction coupled reduction, respectively. Besides, the obtained phosphate and Cr(VI) adsorption data were well described by the Langmuir isotherm and pseudo-second-order kinetic models. Furthermore, the exhausted ZrO2-NaMMT@700 composite could be easily regenerated and reused in subsequent adsorption experiments. Overall, due to the easy synthesis, excellent adsorption capacity, and regeneration ability, the prepared ZrO2-NaMMT@700 composite could be served as a potential candidate for the removal of phosphate and Cr(VI) anions.

Preparation and comparative study of anticorrosion nanocomposites of polyaniline/graphene oxide/clay coating

Abstract In this study, novel anticorrosion coatings including doped polyaniline, reduced graphene oxide (RGO) and modified clay sodium montmorillonite (Na-MMT) were synthesized. The nanocomposite particles were coated on carbon steel after optimal mixing and dispersion in epoxy resin. In order to increase the dispersibility and increase the functional groups between the graphene plates, the initial graphene oxide nanoparticles were re-oxidized and finally reduced to have a better dispersibility in the composite environment. Sodium dodecyl benzene sulfonic acid (SDBS) was used as a secondary dopant and surfactant. Synthesized nanocomposites were characterized using Fourier-transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Furthermore, Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), Fourier-transform infrared spectroscopy (FFT), and salt spray test were used to investigate the electrochemical and anticorrosion behavior of the synthesized composite. The results showed that the initiative of adding certain ratios of RGO and Na-MMT to the polyaniline polymer significantly increased the anticorrosion properties of the coating. It was also found that at the same part ratios, the anticorrosion property of RGO is higher than the anticorrosion property of Na-MMT. According to the Tafel test, the corrosion current of the synthesized nanocomposite was 0.065 μA cm−2, which was lower than the corrosion current of other samples and shows the superiority of the anticorrosion property of this sample. Also, after 720 h of Salt spray test (In 3.5% wt NaCl), a very high and desirable durability of this sample (Sample a) has been observed.

SYNTHESIS AND STRUCTURAL PROPERTIES OF CHITIN/CLAY BIO-NANOCOMPOSITES

Chitin, which is composed of 2-acetamido-2-deoxy-D-glucopyranose (N-acetyl-D-glucosamine) units linked by β-(1,4) linkage, makes up the cell walls of fungi, the exoskeletons of arthropods, such as crustaceans (e.g., crabs, lobsters and shrimps) and insects, the radulae of mollusks, and the beaks of cephalopods, including squid and octopuses. Both chitin and clay are sustainable materials, as they are low cost, biodegradable and readily available. That is why, in this study, sodium montmorillonite (CNa) nanoclay and 1-140 (C15A) organo-nanoclay were used as nanofiller support in the preparation of chitin/clay bio-nanocomposites. Trichloroacetic acid was used to dissolve the chitin and to disperse the clay in the chitin solution. Chitin/CNa and chitin/C15A bio-nanocomposites were synthesized by the solution-induced intercalation method. The effect of the nanofiller on the bio-nanocomposite was investigated by varying the loading rates as follows: 1, 3 and 5% by weight. The composites were characterized by FT-IR, XRD and SEM methods. The XRD patterns and SEM images showed that the clay dispersion in the chitin biopolymer matrix presented an exfoliated structure. It was noted that neither the nanoclay nor the organo-nanoclay used in the synthesis of the bio-composites affected the formation of the exfoliated structure. This result can be attributed to the use of a low amount of clay. These newly synthesized bio-composites, which are environmentally friendly and sustainable, can find application in many different areas in the future.

Polymeric Coatings for AR-Glass Fibers in Cement-Based Matrices: Effect of Nanoclay on the Fiber-Matrix Interaction

Polymeric coatings are widely used to enhance the load bearing capacity and chemical durability of alkali-resistant glass (AR-glass) textile in cement-based composites. The contact zone between coated yarns and concrete matrix plays a major role to enable the stress transfer and has still to be improved for the full exploitation of the mechanical behavior of the composite. As a new approach, this paper studies how the addition of nanoclay particles in the polymer coating formulation can increase the chemical bond between organic coating and inorganic matrix. This includes the description of the water-based coating preparation by dispersing sodium montmorillonites, whereby the resulting coating nanostructure is characterized by X-ray diffraction and energy dispersive X-ray spectroscopy. Single glass fibers were treated by dip-coating. Atomic force microscopy was used to determine the surface roughness, and the effect on the fiber tensile properties was studied. Moreover, the morphological and chemical characteristics of the coatings were compared with the results obtained from single fiber pull-out (SFPO) tests. It was shown that the incorporation of nanoclays leads to increased interfacial shear strength arising from the ability of nanoclay particles to nucleate hydration products in the fiber-matrix contact zone.

Study of a Polyamine Inhibitor Used for Shale Water-Based Drilling Fluid.

Here, we report a water-soluble shale inhibitor for inhibiting shale hydrate formation. The copolymer denoted as thermogravimetric analysis (TGA) was synthesized via triethanolamine, two maleic anhydrides, and glacial acetic acid. The infrared (IR) and gas chromatography (GC) results indicated that TGA is a low molecular weight polymer inhibitor (IR) and is the most commonly used method to identify compounds and molecular structures qualitatively. It is mainly used to study the molecular structure of organic substances and conduct qualitative and quantitative analyses of organic compounds. The main function of GC is for polymer molecular weight analysis. With the aid of shale rolling recovery experiments, particle size distribution experiments, triaxial stress experiment methods, bentonite slurry rate inhibition experiments, and thermogravimetric experiments to evaluate TGA inhibition characteristics, the inhibition effect of TGA is better than that of the traditional inorganic salt inhibitor KCl, polymer amine inhibitor UHIB, and organic cationic shale inhibitor NW-1. When the mass fraction is 0.2%, the cutting recovery rate increases from 18.3 to 94.1%. The compressive strength of the shale core after adding 1% TGA inhibitor is 177.9 MPa, which is close to the original core compressive strength of 186.5. The wet sodium montmorillonite crystal layer spacing after treatment with 0.5%, 1.5%, and 3% TGA aqueous solution is 1.38, 1.35, and 1.35 nm, respectively, and the sodium montmorillonite crystal layer spacing after diesel treatment is 1.34 nm, indicating that the inhibitory effect of TGA on sodium montmorillonite is equivalent to that of diesel and that TGA can effectively inhibit the hydration and dispersion of sodium montmorillonite. At the same time, the crystal layer spacing and the weight loss rate of sodium montmorillonite modified by TGA inhibitors did not change significantly after adsorption of deionized water, which proved that TGA inhibitors could be adsorbed in the crystal layer space of sodium montmorillonite to inhibit hydration and dispersion of sodium montmorillonite. Field test results show that TGA can significantly improve the inhibition performance of the field drilling fluid, and the effect is better than the strong conventional inhibition water-based drilling fluid system, which solves the problems of wellbore instability and considerable friction in horizontal shale sections and provides a new idea and method for efficient shale gas drilling.

Role of the Interchangeable Cations on the Sorption of Fumaric and Succinic Acids on Montmorillonite and its Relevance in Prebiotic Chemistry.

It has been proposed that clays could have served as key factors in promoting the increase in complexity of organic matter in primitive terrestrial and extraterrestrial environments. The aim of this work is to study the adsorption-desorption of two dicarboxylic acids, fumaric and succinic acids, onto clay minerals (sodium and iron montmorillonite). These two acids may have played a role in prebiotic chemistry, and in extant biochemistry, they constitute an important redox couple (e.g. in Krebs cycle) in extant biochemistry. Smectite clays might have played a key role in the origins of life. The effect of pH on sorption has been tested; the analysis was performed by UV-vis and FTIR-ATR spectroscopy, X-ray diffraction and X-ray fluorescence. The results show that chemisorption is the main responsible of the adsorption processes among the dicarboxylic acids and clays. The role of the ion, present in the clay, is fundamental in the adsorption processes of dicarboxylic acids. These ions (sodium and iron) were selected due to their relevance on the geochemical environments that possibly existed into the primitive Earth. Different mechanisms are proposed to explain the sorption of dicarboxylic acids in the clay. In this work, we propose the formation of complexes among metal cations in the clays and dicarboxylic acids. The organic complexes were probably formed in the prebiotic environments enabling chemical processes, prior to the appearance of life. Thus, the data presented here are relevant to the origin of life studies.

Novel preformed gel particles with controllable density and its implications for EOR in fractured-vuggy carbonated reservoirs

The pre-crosslinked gel particles has been perceived as an important alternative to improve oil recovery from fractured-vuggy carbonate reservoirs. However, it remains a great challenge for the applications in high temperature and high salinity reservoirs. In this context, we firstly developed novel preformed gel particles with controllable density (PGPCD) which can be used at high temperature (140 °C) and high salinity (250 g/L) fractured-vuggy carbonate reservoirs for in-depth profile control and displacement. Then, the swelling property, toughness, injectivity, EOR potential and EOR mechanisms of PGPCD were investigated. Experimental results show that PGPCD has favorable swelling ability, toughness, and controllable density due to the introduction of sodium montmorillonite and modified foamed acrylate rubber (ACM) powders. Moreover, PGPCD has favorable injectivity, and can mitigate water channeling in the form of “filling accumulation”, “bifurcation accumulation”, and “necked accumulation”. After the treatment, PGPCD achieves incremental oil recovery in a range of 16%–26% of original oil in place. Taken together, our findings suggest the role of PGPCD in promoting the incremental oil recovery at high temperature and high salinity reservoirs, especially in fractured-vuggy carbonate bottom water reservoirs.

Synthesis and Inhibitive Mechanism of a Novel Clay Hydration Inhibitor for Water-based Drilling Fluids

In order to solve wellbore instability problem, a novel clay hydration inhibitor PDWC for water-based drilling fluids was synthesized by copolymerization of tris hydroxyethyl diallyl ammonium bromide (THDAB), sodium allyl sulfonate (AS) and methyl methacrylate (MMA) initiated by redox initiation in an aqueous solution. PDWC was characterized by Fourier transform infrared spectroscopy (FT-IR), Gel Permeation Chromatography (GPC) and Thermo-gravimetry-Differential Scanning Calorimetry (TGA-DSC), respectively. Evaluation of experiments indicated that PDWC showed superior clay hydration inhibition ability compared to some polymer and inorganic inhibitors. Characterization methods included particle size analysis, FT-IR, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were utilized to study the inhibition mechanism of PDWC, it was observed that PDWC can be adsorbed on the surface of sodium montmorillonite (Na-MMT) by its hydroxyl functional group, which changed the micro-structure of Na-MMT and made the clay particles increased obviously. However, results of XRD demonstrated that it was difficult for PDWC to enter the inner layer crystal of Na-MMT.

Role of Na+-montmorillonite in the stability of guanine exposed to high-radiation energy in primitive environments: Heterogeneous models

In the context of chemical evolution, in which the formation of compounds of biological importance was the first step toward the origin of life, the stability of organic molecules is an essential consideration in evaluating plausible scenarios for the primitive Earth. In this framework, the behavior of guanine (a nucleobase) under gamma irradiation in three types of systems was studied: guanine in aqueous solution, guanine adsorbed in sodium montmorillonite (clay); and a suspension containing both sodium montmorillonite and guanine, with a guanine concentration such that the molecule occupied all the clay's active sites, but excess guanine also existed in the solution.These systems were exposed to a high-gamma radiation field to highlight the clay's possible role as a protective agent toward ionizing radiation in prebiotic processes. Guanine was analyzed by UV-spectroscopy, and ultra-high-performance liquid chromatography (UHPLC). The clay sample was analyzed by FTIR-ATR spectroscopy and X-ray diffraction (XRD).The obtained results show that the guanine in an aqueous medium decomposed quickly, even at low doses of ionizing radiation. Nonetheless, the molecule is relatively stable when it is adsorbed onto sodium montmorillonite. These results were also evaluated at the molecular level with computer simulation models.

Stereoselective Enhancement of VCD Signals for Intercalation Compounds of Sodium Montmorillonite and Chiral Metal Complexes

Abstract Vibrational circular dichroism (VCD) spectra were recorded for the intercalation compounds of sodium montmorillonite co-adsorbing two kinds of metal complexes, Δ- (or Λ-)[Ru(phen)3]2+ and Λ- (or Δ-)[Ni(phen)3]2+. The complexes were chosen so as to form a pseudo racemate. Notably some of the VCD signals were enhanced in comparison to the samples adsorbing each complex separately. The results were rationalized in terms of the delocalization of vibrational motions over a tightly bound molecular pair in a coherent way. The model of racemic adsorption of [M(II)(phen)3]2+ (M(II) = a divalent metal ion) in the interlayer space of a clay mineral was proposed.

Nanocomposite Polymer Electrolytes of Sodium Alginate and Montmorillonite Clay.

Nanocomposite polymer electrolytes (NPEs) were synthesized using sodium alginate (Alg) and either sodium (SCa-3-Na+)- or lithium (SCa-3-Li+)-modified montmorillonite clays. The samples were characterized by structural, optical, and electrical properties. SCa-3-Na+ and SCa-3-Li+ clays’ X-ray structural analyses revealed peaks at 2θ = 7.2° and 6.7° that corresponded to the interlamellar distances of 12.3 and 12.8 Å, respectively. Alg-based NPEs X-ray diffractograms showed exfoliated structures for samples with low clay percentages. The increase of clay content promoted the formation of intercalated structures. Electrochemical Impedance Spectroscopy revealed that Alg-based NPEs with 5 wt% of SCa-3-Na+ clay presented the highest conductivity of 1.96 × 10−2 S/cm2, and Alg with 10 wt% of SCa-3-Li+ showed conductivity of 1.30 × 10−2 S/cm2, both measured at 70 °C. From UV-Vis spectroscopy, it was possible to infer that increasing concentration of clay promoted a decrease of the samples’ transmittance and, consequently, an increase of their reflectance.

Effect of interfacial interactions on static and dynamic behavior of hyperbranched polymers: Comparison between different layered nanoadditives

The structure and dynamics of a hyperbranched poly (ester amide) and its nanocomposites with natural sodium montmorillonite (Na+-MMT) and graphite oxide (GO) are investigated to provide an understanding of the influence of different polymer-inorganic interfacial interactions on the polymer behavior. In both systems, the favorable interactions lead to intercalated structures; however, the different interaction strengths create polymer nanofilms of different thicknesses between the inorganic layers. The composition of the nanohybrids is such that all chains are expected to reside within the galleries of the nanoadditives. Thermal reduction of GO in the presence of the polymer forces the system to lose its periodic structure; nevertheless, the deoxygenation temperature decreases in the presence of the polymer when compared to the respective one for the bare GO. At the same time, the thermal stability of the polymer decreases in the presence of GO. In both cases, the glass transition of the intercalated chains is fully suppressed. The different surface interactions affect polymer dynamics by modifying the number of relaxation processes, their relaxation times which become faster or slower than the bulk, as well as the temperature dependencies of the processes.

Gelatin Films Activated by Cinnamon Essential Oil and Reinforced with 1D, 2D and 3D Nanomaterials: Physical and Release Controlling Properties

The aim of this study was to assess the effect of sodium montmorillonite (MMT), cellulose nanofibers (CNF) and titanium dioxide nanoparticles (TiO2NPs) on the physicochemical properties and release profile of the gelatin-based film activated with cinnamon essential oil (CEO). The results of FT-IR, XRD, FE-SEM and tensile analysis showed that the incorporation of nanofillers caused to different changes in the morphology, crystalline structure, and mechanical properties of gelatin films that were correlated with their morphology. The water barrier properties of films significantly increased by incorporation of nanofillers and MMT had the highest improving effect. As results of release profile study, MMT incorporated active film exhibited the slowest release rate with the lowest diffusion coefficient (8.67 ± 0.52 × 10−8cm2 s−1 at 25 °C), and highest activation energy (14.87 ± 1.11 kJ mol−1). In conclusion, nanolayers such as MMT were suggested as the best candidate to use as simultaneous reinforcement and release controlling agent in the activated biopolymer-based films.

Flexible and self-healable poly (N, N-dimethylacrylamide) hydrogels for supercapacitor prototype

Flexible, and self-healable supercapacitors possess significant advantages over liquid electrolyte based supercapacitors. Liquid electrolytes are usually organic and not environmentally friendly. Therefore, flexible water-based electrolyte is a reliable choice. Water-based hydrogel electrolyte is a novel approach to overcome liquid electrolyte related drawbacks. In this study, we propose physically crosslinked poly (N, N-dimethylacrylamide) hydrogel using sodium montmorillonite as a crosslinking agent. The hydrogel electrolytes are prepared by adding different weight % (wt.%) of magnesium trifluoromethanesulfonate (MgOTf) salt as a source of ions. The synthesized hydrogel and hydrogel electrolytes are characterized via functional group identification, thermal decomposition, surface morphology, and elemental composition. Fourier transform infrared (FTIR) deconvolution and transference number measurement are conducted to confirm the complexation and ionic species. Based on the surface morphology, FTIR, and transference number measurement, it could be deduced that enhanced ionic conductivity is due to the amorphous nature of hydrogel electrolyte. Furthermore, an ionic conductivity study revealed that hydrogel electrolyte formulated by adding 30 wt.% salt (DMA3) attained maximum ionic conductivity of 6.69 × 10−3 S/cm. The electrochemical characterization of fabricated symmetric supercapacitor described that AC/DMA3/AC achieved the highest specific capacitance of 119 F/g at 3 mV/s and 142 F/g at 50 mA/g along with 98.07 % capacitance retention at 4 A/g after 5000 consecutive charge-discharge cycles. In addition, a flexible prototype supercapacitor device was designed using two symmetrical optimized AC/DMA3/AC cells connected in series, charged with external power supply, and lighted up the light-emitting diode (LED). The self-healability of the prototype was also examined. Results are very promising for the development of compact, self-standing, self-healable, highly flexible, lightweight, and biocompatible supercapacitors.

Effect of Na- and Organo-Modified Montmorillonite/Essential Oil Nanohybrids on the Kinetics of the In Situ Radical Polymerization of Styrene.

The great concern about the use of hazardous additives in food packaging materials has shown the way to new bio-based materials, such as nanoclays incorporating bioactive essential oils (EO). One of the still unresolved issues is the proper incorporation of these materials into a polymeric matrix. The in situ polymerization seems to be a promising technique, not requiring high temperatures or toxic solvents. Therefore, in this study, the bulk radical polymerization of styrene was investigated in the presence of sodium montmorillonite (NaMMT) and organo-modified montmorillonite (orgMMT) including thyme (TO), oregano (OO), and basil (BO) essential oil. It was found that the hydroxyl groups present in the main ingredients of TO and OO may participate in side retardation reactions leading to lower polymerization rates (measured gravimetrically by the variation of monomer conversion with time) accompanied by higher polymer average molecular weight (measured via GPC). The use of BO did not seem to affect significantly the polymerization kinetics and polymer MWD. These results were verified from independent experiments using model compounds, thymol, carvacrol and estragol instead of the clays. Partially intercalated structures were revealed from XRD scans. The glass transition temperature (from DSC) and the thermal stability (from TGA) of the nanocomposites formed were slightly increased from 95 to 98 °C and from 435 to 445 °C, respectively. Finally, better dispersion was observed when orgMMT was added instead of NaMMT.