MMT Nanosheets Research Articles

Gelatin/montmorillonite biohybrid films prepared via a novel photocrosslinking method: structure–properties investigations

Gelatin/sodium montmorillonite (Na+MMT) hybrid nanocomposite films were prepared by a new photocrosslinking method using 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone (Irgacure 2959) as a photoactive radical initiator and N,N′-Methylenebisacrylamide (MBA) as a crosslinking agent. The prepared samples were characterized by X-ray diffraction (XRD), differential scanning calorimetry, stress–strain measurements and UV–Vis spectrophotometry. XRD patterns showed the formation of exfoliation structure resulting in considerable improves in mechanical properties of the nanocomposite. Retaining of transparency also suggested that Na+MMT nanosheets were uniformly distributed in the gelatin matrix. The tensile strength and Elastic’s modulus of nanocomposites were also improved notably by enhancing amount of Na+MMT. Furthermore, gelatin/Na+MMT nanocomposites showed a second T g at a higher temperature in presence of Na+MMT.

Flame retardant and hydrophobic coatings on cotton fabrics via sol-gel and self-assembly techniques

Nanocoatings consisting of ammonium polyphosphate (APP), sodium montmorillonite (MMT), and vinyltrimethoxysilane (VTMS) were prepared via self-assembly and in situ sol-gel techniques and applied onto cotton fabrics to achieve both flame retardancy and hydrophobicity. The impacts of APP concentration on the hydrophobicity and fire resistance of the coated fabrics were investigated. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) characterization results verified the hydrolysis-condensation reaction of VTMS and the formation of Si-O-Si network structure. X-ray diffraction (XRD) proved the formation of a layered structure based on MMT nanosheets in the coatings. Both vertical flame test (VFT), limiting oxygen index (LOI), thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC) characterization were conducted to evaluate the flame retardancy, thermostability and heat release behavior of the coated cotton fabrics, respectively. The results suggested that a higher concentration of APP is beneficial for both hydrophobicity and flame retardancy of the coated substrates. Overall, our research provides a facile and very effective approach to prepare flame retardant and hydrophobic multifunctional coating for cotton fabric and other substrates.

Novel Luminescent Multilayer Films Containing π-Conjugated Anionic Polymer with Electronic Microenvironment

Layered double hydroxides (LDHs), luminescent π-conjugated anionic polymer and montmorillonite (MMT) were orderly assembled into luminescent multilayer films via layer-by-layer self-assembly method. The electronic microenvironment (EME), the structure of which is like a traditional capacitor, can be constructed by exfoliated LDHs or MMT nanosheets. In addition, the rigid inorganic laminated configuration can offer stable surroundings between the interlayers. As a result, we conclude that EME can extend the luminescent lifespans of multilayer films substantially, due to affecting relaxation times of π-conjugated anionic polymer. Consequently, because of the remarkable impact on better photoemission behaviors of luminescent π-conjugated anionic polymer, EME assembled by LDHs or MMT nanosheets have had high hopes attached to them. They are expected to have the potential for designing, constructing, and investigating novel light-emitting thin films.

Novel nanocomposite super absorbent polymers reinforced by clay nanosheets

Super absorbent polymers (SAPs) are of great significance in industry and personal care, etc. The study aims to introduce novel nanocomposite SAPs that are able to uptake very high water content while maintaining excellent strength. The polymers are synthesized by in situ polymerization with the presence of exfoliated montmorillonite (MMT) and trace amount of crosslinkers. SEM images show macroporous structures of these nanocomposites, while TEM images demonstrate excellent distribution of the MMT nanosheets in the polymer matrix. The effect of clay content on the equilibrium water uptake has been systematically investigated. More importantly, the highly swollen nanocomposite SAPs show very high tensile strength (up to 550 kPa), which is much higher than those reported in literature and used in the market. These SAPs with high water uptake and strength may find applications in agriculture and oil fields.

Sandwichlike Coating Consisting of Alternating Montmorillonite and β-FeOOH for Reducing the Fire Hazard of Flexible Polyurethane Foam

A novel nanocoating, composed of montmorillonite (MMT) nanosheets and β-FeOOH nanorods, was deposited on the surface of flexible polyurethane (FPU) foams through a layer-by-layer assembly technique to reduce its flamability. The coating growth was performed by alternately immersing FPU foams into polyethylenimine (PEI) solution, MMT-alginate suspension, and β-FeOOH dispersion. Structural and morphological characterization indicated that MMT nanosheets and β-FeOOH nanorods were distributed homogeneously on the surface of the matrix and formed a sandwichlike topology. The coated FPU foams showed the lower peak heat release rate (PHRR), compared to the counterparts fabricated by introduction of MMT nanosheets or β-FeOOH nanorods alone. Furthermore, the concentration of volatile products released from the coated FPU foams was reduced remarkably, indicating that the binary components had tremendous advantages in reducing the flamability of the material. These significant improvements in flame retardancy and to...

Layer-by-layer assembly of luminescent multilayer thin films by MMT, anionic chromophores and magnetic CoAl-LDHs nanosheets

In this report, luminescent multilayer thin films (MTFs) based on oppositely-charged montmorillonite (MMT) and transition metal-bearing layered double hydroxides (LDHs) nanosheets were fabricated via a layer-by-layer assembly method. Oppositely-charged inorganic nanosheets can be expected to assemble an electronic microenvironment (EME), and transition metal-bearing LDHs nanosheets can offer an additional magnetic field (MF) for the chromophores at the same time. Surprisingly, the luminescent lifetimes of MTFs with EME and MF are significantly prolonged compared with that of the pristine chromophores, even much longer than those of MTFs without oppositely-charged and magnetic architecture. Therefore, it is highly expected that the EME and MF formed by oppositely-charged and transition metal-bearing inorganic nanosheets have remarkable influence on enhancing the luminescent lifetimes of chromophores, which suggest a new potential way to manipulate, control and develop the novel light-emitting materials and optical devices at molecular level.

Nacre-inspired integrated nanocomposites with fire retardant properties by graphene oxide and montmorillonite

Bioinspired ternary rGO–MMT–PVA nanocomposites were successfully fabricatedviathe synergistic toughening effect from building blocks of GO and MMT nanosheets.

Fabrication of a novel “loose” nanofiltration membrane by facile blending with Chitosan–Montmorillonite nanosheets for dyes purification

The novel hybrid material, clay/polymer nanocomposite has represented a desired alternative for designing the mixed matrix membranes (MMMs) due to their excellent overall performance, such as good hydrophilic nature, high mechanical strength, enhanced thermal stability, etc. In this study, we report a feasible method to fabricate a novel “loose” nanofiltration membrane by blending with Chitosan–Montmorillonite (CS–MMT) nanosheets via phase inversion method. The results of FT-IR, XRD and TEM showed that CS–MMT nanosheets were successfully fabricated. It was found that the hydrophilicity and water flux of hybrid membranes greatly improved after adding CS–MMT nanosheets. Meanwhile, the hybrid membranes exhibited a preferable antifouling property, that is, high flux recovery ratio (ca. 92%) and low total flux decline ratio (ca. 0.26) when CS–MMT content was only 1.0wt.%. Additionally, CS–MMT nanosheets provided an enhanced mechanical property, thus giving rise to significant promotion in both tensile strength and elongation at break of the hybrid membranes. More importantly, the “loose” nanofiltration membrane showed higher rejection for Reactive Black 5 and Reactive Red 49, and lower rejection for bivalent salts unlike the conventional nanofiltration membranes. Therefore, the “loose” nanofiltration membrane could be used for dyes purification with low pressure and high efficiency.

Simultaneously Boosting Toughness and Tensile Strength for Polyamide 6/montmorillonite Nanocomposite by a Pressure-Induced Flow Field

Nanocomposites of polymers and montmorillonite (MMT) represent a type of important hybrid material. However, unlike in some natural hybrid materials where much improved mechanical properties are achieved by an ordered assembly (layered, sheet-like or fibrous morphology) of complementary hard and soft components on nano- and microscopic scales, the exfoliated MMT nano-sheets are generally randomly dispersed in bulk polymeric matrices. In this paper we utilized a pressure-induced flow (PIF) field to orient MMT nano-sheets and generate stratified morphologies in polyamide 6 (PA6)/MMT nanocomposite bulk material. The toughness and tensile strength can be simultaneously increased. In particular, the impact strength increased up to 10 fold higher than the same material obtained by conventional processing methods. The mechanism for enhancement could be the confinement of crack propagations and the tortuous energy dissipating paths, which are attributed to the oriented MMT and the anisotropic hierarchical morphologies formed during PIF-processing.

Covalent linking of quantum dots to polymer for inorganic-inorganic luminescence films via layer-by-layer assembly with clay.

Herein, positively charged QDs were initially prepared by covalently linking to poly(allylamine hydrochloride) (PAH). The resulting PAH-modified QDs in conjunction with MMT nanosheets were utilized to fabricate QDs/MMT UTFs via LBL assembly. Strong photoluminescence, temperature responsiveness, long-term stability and high uniformity make these films potential candidates for a wide range of applications.

Structural characterization of hydrophilic polymer blends/montmorillonite clay nanocomposites

ABSTRACTThe nanocomposite films comprising polymer blends of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO), and poly(ethylene glycol) (PEG) with montmorillonite (MMT) clay as nanofiller were prepared by aqueous solution casting method. The X‐ray diffraction studies of the PVA–x wt % MMT, (PVA–PVP)–x wt % MMT, (PVA–PEO)–x wt % MMT and (PVA–PEG)–x wt % MMT nanocomposites containing MMT concentrations x = 1, 2, 3, 5 and 10 wt % of the polymer weight were carried out in the angular range (2θ) of 3.8–30°. The values of MMT basal spacing d001, expansion of clay gallery width Wcg, d‐spacing of polymer spherulite, crystallite size L and diffraction peak intensity I were determined for these nanocomposites. The values of structural parameters reveal that the linear chain PEO and PEG in the PVA blend based nanocomposites promote the amount of MMT intercalated structures, and these structures are found relatively higher for the (PVA–PEO)–x wt % MMT nanocomposites. It is observed that the presence of bulky ester‐side group in PVP backbone restricts its intercalation, whereas the adsorption behavior of PVP on the MMT nanosheets mainly results the MMT exfoliated structures in the (PVA–PVP)–x wt % MMT nanocomposites. The crystallinities of the PEO and PEG were found low due to their blending with PVA, which further decreased anomalously with the increase of MMT concentration in the nanocomposites. The decrease of polymer crystalline phase of these materials confirmed their suitability in preparation of novel solid polymer nanocomposite electrolytes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40617.

The Preparation and Characteristics of MMT Nanosheets

Montmorillonite (MMT) mainly consist of hydrated aluminum silicate. Montmorillonite has particular properties and many practical applications, because of their special crystal structure. Here, mechano-chemical method was used to prepare MMT nanosheets by controlling the pH value. MMT nanosheets were obtained by ballmilling, and the impact of pH value on the nanosheets preparing was studied. TEM was employed to emamine the microstructure of MMT nanosheets. The size are analyzed to study the status of MMT nanosheets. Different rare earth ions as a fluorescence center were assembled on nanosheets，and composites were obtained. The luminescent properties of composite materials were studied.

Exfoliation of montmorillonite by the insertion of disklike micelles via the soap‐free emulsion polymerization of methyl methacrylate

AbstractMontmorillonites (MMTs) intercalating a potassium persulfate initiator were readily exfoliated in the presence of polymerizing methyl methacrylate during soap‐free emulsion polymerization. Because of the confined space, the polymerizing chains were aggregated into a disk form inside the clay interlayer regions for micellation. It was surprising to find from X‐ray diffraction analysis that the exfoliation of MMT was almost completed in the micellation stage. Further polymerization afforded latex particles of exfoliated poly(methyl methacrylate) (PMMA)–MMT nanocomposites. In addition, two kinds of MMT nanosheets were collected by the removal of PMMA with toluene: One was a single‐layer nanosheet with a thickness of 1.25 nm, and the other was a stacked sheet with an average thickness of 7.5 nm that may have consisted of six individual layers. Electron diffraction analysis revealed that if the individual layer of an MMT nanosheet were not a single crystal, it should contain an ultrathin layer of ice with a commonly occurring hexagonal phase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5572–5579, 2006