Galleries Of Montmorillonite Research Articles

Natural Rubber Nanocomposites With Organo-Modified Bentonite

AbstractEnhancement of the physico-chemical properties of elastomers can be achieved by the addition of fillers, such as silica, but the search for less expensive alternative materials continues. The objective of this study was to investigate natural or organically modified clay minerals as such an alternative. Organo-clays modified by quaternary ammonium cations with three methyl groups and longest alkyl chains of different lengths were prepared by ion-exchange reaction of the commercial product JP A030 (Envigeo, Slovakia) based on Jelšový Potok bentonite with organic salts: tetramethylammonium (TMA) chloride, octyltrimethylammonium (OTMA) bromide, and octadecyltrimethylammonium (ODTMA) bromide. Physico-chemical characterizations of the organo-clays used as fillers in rubber nanocomposites and their mechanical properties were measured using Fourier transform infrared (IR) spectroscopy, which provided information on the chemical composition of the mineral and on the amount of organic moieties adsorbed. X-ray diffraction analysis (XRD) was used to monitor the arrangement of organic chains in galleries of montmorillonite and showed that the longest-chain alkylammonium ODTMA+ ions were intercalated between layers, adopting a pseudotrimolecular conformation, while OTMA+ and TMA+ were in monomolecular arrangement. Surface areas were measured by sorption of N2 and ethylene glycol monoethyl ether. Natural rubber-clay nanocomposites were prepared by melt intercalation, in some cases also with addition of silica, a conventional reinforcing filler. The microstructure of montmorillonite in these composites was characterized by XRD analysis. The effect of clay and organo-clays loading from 1 to 10 phr (parts by weight per hundred parts of rubber) on stress at break, strain at break, and Modulus 100 (M100) was investigated by tensile tests. Filler ODTMA-JP A030 appears to be the most effective among the organoclays; surprisingly similar values of composite elongation and strength were obtained with unmodified bentonite JP A030.

Preparation and characterization of 3-aminopropyltriethoxysilane grafted montmorillonite and acid-activated montmorillonite

3-aminopropyltriethoxysilane grafted montmorillonites were synthesized with montmorillonite, acid-activated montmorillonites and 3-aminopropyltriethoxysilane in ethanol-water mixture. The resulting products were investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TG). XRD patterns demonstrated that silane was intercalated into the montmorillonite gallery, indicated by increasing basal spacings. These intercalated silanes probably adopt bilayer arrangement models within the montmorillonite and acid-activated montmorillonites interlayer spaces. TG and DTG curves indicate that acidification results in a decrease of the thermal stability of the resultant montmorillonites. Silane grafting leads to a surface property transformation of montmorillonite from hydrophilicity to lipophilicity and an increase of the thermal stability of the condensed silanes.

Renewable Polymeric Nanocomposite Synthesis Using Renewable Functionalized Soybean-Oil-Based Intercalant and Matrix

Completely bio-based and renewable polymeric nanocomposites have been prepared using an in situ polymerization technique in the presence of organically-modified montmorillonite (MMT) clays in different loading degrees. Acrylated epoxidized soybean oil (AESO) and styrene have been used as matrices, whereas modification of MMT has been done by using a new renewable soybean-oil-based intercalant, quarternized functionalized acrylated epoxidized soybean oil, which is the first renewable intercalant described in the literature. It was found that the above-mentioned intercalant could be successfully intercalated between the interlayer galleries of montmorillonite which is confirmed by X-ray diffraction (XRD) data and atomic force microscopy (AFM). The nanocomposite formation studies examined by both XRD and AFM showed that the desired exfoliated nanocomposite structures can be achieved with all nanofiller loadings. The resultant exfoliated nanocomposites were found to have significantly improved thermal stability and dynamic mechanical performance at very low loadings. The nanocomposites from both renewable intercalant and matrix offer a significant potential for new high-volume, low-cost applications.

Grafting of montmorillonite with different functional silanes via two different reaction systems

Silane grafted montmorillonites were synthesized by using 3-aminopropyltriethoxysilane and trimethylchlorosilane via two different grafting reaction systems: (a) ethanol–water mixture and (b) vapor of silane. The resulting products were investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA). XRD patterns demonstrate that silane was intercalated into the montmorillonite gallery, as indicated by the increase of the basal spacing. The product prepared by vapor deposition has a larger basal spacing than that obtained from solution, due to the different extent of silane hydrolysis in various grafting systems. TGA curves indicate that the methyl groups penetrate into the siloxane clay are the primary reason for the decrease of the dehydroxylation temperature of the grafted products. 3-Aminopropyltriethoxysilane in the grafted montmorillonite adopts a bilayer arrangement while trimethylchlorosilane adopts a monolayer arrangement within the clay gallery.

Montmorillonite (MMT) effect on the structure of poly(oxyethylene) (PEO)–MMT nanocomposites and silica–PEO–MMT hybrid materials

In this work we report the effects of incorporation of variable amounts (0.5–25%w/w) of montmorillonite in poly(oxyethylene) based materials in order to decrease the polymer crystallinity. Two different classes of materials were studied: silica-poly(oxyethylene)-montmorillonite hybrids prepared by the sol–gel route and poly(oxyethylene)-montmorillonite nanocomposites prepared by mixing the dry clay or the clay aqueous suspension into the melt poly(oxyethylene). The effects of montemorillonite loading on the poly(oxyethylene) crystallization control and on the nanostructural features were investigated by X-ray powder diffraction, small-angle X-ray scattering and differential scanning calorimetry. Experimental results show that free montmorillonite layers coexist with open aggregates and tactoids in the poly(oxyethylene)-montmorillonite nanocomposites, with different features depending on the filler proportion and preparation route. The intercalation of polymer chains in montmorillonite galleries markedly hinders the crystallization of the poly(oxyethylene) matrix. For hybrids materials the silica phase favors the exfoliation of montmorillonite tactoids, so that samples are predominantly constituted by dispersed platelets.

Interaction of functional groups of gelatin and montmorillonite in nanocomposite

AbstractAs an amphoteric polyelectrolyte, gelatin could intercalate into the galleries of montmorillonite (MMT). In this paper, sodium laurate/MMT composites and sodium laurate/dehydroxylated MMT composites were introduced as low molecular simulation to investigate the interaction functional groups of gelatin and MMT. The composites were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and 13C nuclear magnetic resonance (13C NMR). Furthermore, the effect of interaction between gelatin and MMT on the mechanical properties of the composites was investigated. The results indicated that COO−, not COOH, in gelatin chains could interact strongly with the MMT sheets. The reactive sites on MMT were hydroxyl groups, which could interact with COO− in gelatin chains by forming hydrogen bonds. The gelatin/MMT composites prepared in alkalic media have better mechanical properties due to stronger interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1556–1561, 2006

SYNTHESIS AND CHARACTERIZATION OF POLY(BUTYL ACRYLATE-CO-METHYL METHACRYLATE)/CLAY NANOCOMPOSITES VIA EMULSION POLYMERIZATION

Poly(butyl acrylate-co-methyl methacrylate)/clay nanocomposites were synthesized via emulsion polymerization with an emulsifier (sodium dodecyl benzene sulfonate, SDBS), an initiator (ammonium persulate, APS), acrylic acid ester monomer and Na -montmorillonite. It was found that the addition of SDBS and water widened the gap between clay layers and facilitated monomers to penetrate into clay. Through initiator, comonomers were polymerized in the montmorillonite galleries. The structure of extracted nanocomposites was confirmed by XRD, transmission electron microscopy (TEM). Their thermal property and molecule weight were investigated by differential scanning calorimetry (DSC) and gel-penetrate chromatogram (GPC).

Thermal Characterization of Surfactant-Modified Montmorillonites

AbstractThe thermal stability of surfactant-modified clays plays a key role in the synthesis and processing of organoclay-based nanocomposites. Differential thermal analysis (DTA), thermogravimetric measurement and differential scanning calorimetry (DSC) were used in this study to characterize the thermal stability of hexadecyltrimethylammonium bromide-modified montmorillonites prepared at different surfactant concentrations. Analysis by DSC shows that the molecular environment of the surfactant within the montmorillonite galleries is different from that in the bulk state. The endothermic peak at 70–100°C in the DTA curves of the modified montmorillonites is attributed to both the surfactant phase transformation and the loss of free and interlayer water. With an increase of surfactant-packing density, the amount of water residing in the modified montmorillonite decreases gradually, reflecting the improvement of the hydrophobic property for the organoclay. However, the increase in the surfactant packing density within the galleries leads to a decrease in the thermal stability of the organoclays.With an increase of initial surfactant concentration for the preparation of organoclays, the surfactant- packing density increases gradually to a ‘saturated’ state. It was found that the cationic surfactant was introduced into the montmorillonite interlayer not only by cation exchange but also by physical adsorption.

Insertion of Polypyrrole Chains into Montmorillonite Galleries by a Solvent‐Free Mechanochemical Route

AbstractSummary: Non‐ionic pyrrole was directly intercalated into unmodified montmorillonite (MMT) and organically modified MMT galleries by adsorption, and subsequently polymerized within the interlamellar spaces by a mechanochemical route under solvent‐free conditions. XRD analysis revealed the successful intercalation of pyrrole into unmodified MMT and organically modified MMT clay galleries by mechanochemical grinding. After in situ polymerization, the XRD and FT‐IR analyses confirmed the insertion of polypyrrole chains between both MMT galleries.X‐ray powder diffraction patterns of (A) pyrrole‐intercalated MMT and (B) pyrrole‐intercalated C18‐MMT.imageX‐ray powder diffraction patterns of (A) pyrrole‐intercalated MMT and (B) pyrrole‐intercalated C18‐MMT.

Interlayer structure of organically modified montmorillonites: Effect of surfactant loading

The surfactant cetyltrimethylammonium ion (CTA+) was confined within the galleries of montmorillonite (MMT) to obtain a series of organo-montmorillonites (C16-MMTs) through an ion-exchange intercalation reaction. The C16-MMT formed a single precipitate layer when CTA+ loading was 18.3 wt% but stratified at high loadings. The conformational disorder increased with increasing CTA+ loading. The upper precipitate was characterized by a larger gallery height and a higher surfactant loading in comparison with lower precipitate. The confined methylene chains adopted a lateral monolayer with a small percentage of conformation freedoms at CTA+ loading of 18.3 wt%. The intercalated methylene chains were arranged either in a lateral monolayer or in a tilted interdigitated bilayer at CTA+ loading of 24.7 wt% while in either a tilted interdigitated bilayer or a lateral bilayer at high CTA+ loadings. The different arrangements of methylene chains intercalated in the MMT galleries are believed to be the reason for the stratification.

Cyanate ester polymerization catalysis by layered-silicates

This work examines the effect of Na montmorillonite (Na MMT) and cation exchanged layered montmorillonite on the polymerization of a cyanate ester monomer (1,1-bis(4-cyanatophenyl)ethane). The cyanate ester polymerization reaction is examined using a traditional catalyst and several montmorillonites. Thermal properties of the liquid monomer mixtures and final polymers were investigated, along with the montmorillonite structural changes that occur during the various stages of polymerization. It was found that Na montmorillonite catalyzed the polymerization reaction and that the catalytic activity increased upon sodium cation exchange in the montmorillonite gallery. Montmorillonite catalyzed systems were found to have superior properties (cross-link homogeneity and extent of polymerization) compared to traditionally catalyzed cyanate ester-montmorillonite polymers. Evidence suggests that the montmorillonite structure is a mixture of exfoliated layers and intercalated tactoids. The intercalated montmorillonite was found to undergo a two-step layer expansion process beginning with monomer permeation into the gallery, followed by expansion possibly caused by monomer/polymer reorientation within the gallery.

Preparation and characterization of new difunctional cationic radical initiator-montmorillonite hybrids

Three different radical azo-initiators, containing quaternary ammonium moieties, were synthesized from 2,2′-azobis[2-methyl- N-(2-hydroxyethyl)] propionamide. These initiators were intercalated into the galleries of montmorillonite (MMT), via cationic exchange, in order to obtain the radical initiator-MMT hybrids. The azo-initiators have dual functions: modifying MMT to be organophilic, and initiating the polymerization of vinylic monomers. The sizes of the intercalated initiators in the clay galleries were closely related to the interlayer d-spacing of their corresponding initiator-MMT hybrid. The swelling of the initiator-MMT hybrids was also tested towards various polar and non-polar monomers. Based on the interlayer d-spacing, and the swelling of the hybrids, 2,2′-azobis{2-methyl- N-[2-acetoxy-(2- N, N, N-tributylammonium bromide) ethyl] propionamide}-MMT was found to be the best of the radical initiator-MMT hybrids tested, especially for the non-polar monomers.

Conformation of Surfactant Molecules in the Interlayer of Montmorillonite Studied by 13C MAS NMR

AbstractThe ordering conformation of surfactant molecules in intercalated montmorillonite prepared at various concentrations was investigated by 13C MAS NMR. The 13C MAS NMR study demonstrates the coexistence of ordered and disordered chain conformations. Two main resonance peaks are associated with the backbone alkyl chains: the resonance at 33 ppm corresponds to the ordered conformation (all-trans), and the resonance at 30 ppm corresponds to the disordered conformation (mixture of trans and gauche). Deconvolution of 13C MAS NMR spectra indicates that the ordering conformation of surfactant molecules within the gallery of montmorillonite depends very much on their orientation and packing density. When amine chains are oriented parallel to the silicate layers, the amount of all-trans conformer decreases with the increase of amine concentration. However, the amount of all-trans conformer increases with the increase of amine concentration when amine chains radiate from the silicate layers. Furthermore, 13C MAS NMR spectra show that the intercalated surfactant molecules in the clay minerals never attained the complete liquidlike or solidlike behavior.

Infrared study of HDTMA + intercalated montmorillonite

In this paper, FTIR spectroscopy using attenuated total reflection (ATR) and KBr pressed disk techniques has been used to characterize sorbed water and HDTMA + in organo-clay. Sorbed water content decreases with the intercalation of HDTMA +. With the decrease of the sorbed water content, the position of the ν 2 mode shifts to higher frequency dramatically while the stretching vibration shifts to lower frequency slightly, indicating that H 2O is less strongly hydrogen bonded. This might be resulted from the polarization of H 2O molecules by the changeable cations and HDTMA +. FTIR spectra show that both antisymmetric and symmetric CH 2 stretching absorption bands shift to low frequencies with increase of amine concentration within the galleries of montmorillonite, elucidating the increase of ordered conformation. Furthermore, the present study demonstrates that the antisymmetric CH 2 stretching mode is more sensitive to the conformational ordering than the symmetric stretching mode. When KBr pressed disk technique used, two well resolved absorption bands at 730 and 720 cm −1, and at 1473 and 1463 cm −1, corresponding to the methylene scissoring and rocking modes, respectively, could be observed in FTIR spectra of organo-clays with relative higher concentration of surfactant. However, the FTIR spectra using ATR technique only display singlets and they are independent of amine concentration and chain conformation. Our present study demonstrates that FTIR spectroscopy using KBr pressed disk technique is more suitable to probe the conformational ordering of surfactant in organo-clays than that suing ATR technique does.

Exfoliable organo-montmorillonite nano-fillers for polymer/ceramic composites

The preparation of exfoliable organo-montmorillonites, usable as nano-fillers in polymer-matrix composites, was studied. Such fillers are able, when added in amounts of less than 10%, to improve dramatically the engineering properties of various polymer matrices. Here, both neutral and cationic amine molecules were inserted in the silicate's gallery. The added molecules modify the water and sodium content of the gallery and also its height. The molecules' electrical state, structure and the organics/smectite ratio in the reactor, profoundly influence the characteristics of the resulting organo-montmorillonite. It was found that long chain amines, in the ionic state, are, in contrast to the short ones, able to expand substantially the montmorillonite gallery. When present in large amounts, such amines adopt, within the gallery space, arrangements which favor a height increase. Cationic state amines, aided by exchange reactions with the gallery cations, penetrate much more easily into the gallery than do neutral molecules. Practically attractive preparation technologies may be based on the use of cationic amine molecules which allow the reproducible preparation of nano-fillers, exhibiting gallery heights of ∼20–26 Å, with relative ease. Such products are stable up to 280 °C.

Novel acidic porous clay heterostructure with highly ordered organic–inorganic hybrid structure: one-pot synthesis of mesoporous organosilica in the galleries of clay

A new class of organic–inorganic hybrid porous clay heterostructures (HPCHs) have been prepared through the surfactant-directed assembly of organosilica in the galleries of montmorillonite. The reaction involved hydrolysis and condensation of phenyltriethoxysilane and tetraethoxysilane in the presence of intragallery surfactant templates (dodecylame and cetyltrimethylammonium ion). The surfactant templates were removed from the pores by solvent-extraction. The products were characterized by X-ray diffraction (XRD), N 2 adsorption, solid-state 29Si and 13C NMR, and FTIR. XRD patterns indicated a regular interstratification of the clay layers for HPCHs. Depending on loading of phenyl groups, HPCHs had BET surface areas of 390–771 m 2 g −1, pore volumes of 0.3–0.59 cm 3 g −1, and the framework pore sizes in the supermicropore to small mesopore range (1.2–2.6 nm). HPCHs were hydrophobic and acidic.

Surface modifications of montmorillonite for tailored interfaces in nanocomposites

Different kinds of clays based on sodium montmorillonite have been modified by (1) cationic exchange of alkylammonium ions and (2) covalent grafting of organosilane. We have prepared organophilic clays with different gallery heights (due to alkylammonium ions with alkyl chain length varying from 8 to 18 carbon atoms) and with a specific functionalization (due to the organosilane). The experimental parameters of the cationic exchange process (exchange temperature, initial amine/clay ratio, washing of the clay) govern the quantity of the intercalated alkylammonium ions as well as their organization in the montmorillonite galleries. We have generated organoclays with different kinds of organic layer properties, namely ionically bonded or physically adsorbed alkylammonium ions and covalently grafted organosilane. These different surface treatments will be useful for different applications, varying as a function of the coupling with the matrix and as a function of filler dispersion and resulting properties (thermal stability, mechanical and barrier properties) of the final nanocomposite.

ORGANIC/INORGANIC NANOCOMPOSITES PREPARED BY SPONTANEOUS POLYMERIZATION OF ETHYNYLPYRIDINE WITHIN MONTMORILLONITE

2-Ethynylpyridine was intercalated and polymerized spontaneously within several montmorillonites with different exchangeable cations. FT-IR and UV/vis absorption spectroscopy showed the formation of extensively conjugated polymers within the galleries of montmorillonite. The poly(2-ethynylpyridine) (P2EPy) liberated from montmorillonite has an absorption peak at 470 nm, while P2EPy from thermal polymerization in bulk absorbs at 370 nm, indicating a more extensively conjugated structure of the former. The rate of polymerization within montmorillonites increases in the following order: sodium montmorillonite < calcium montmorillonite < proton montmorillonite. X-ray data support the model of one layer of P2EPy inserted between the lamellae of the aluminosilicate with pyridine rings of the repeating unit oriented nearly perpendicularly to the surface of the lamellae. The intercalated P2EPy within the galleries of montmorillonite displayed an enhanced thermal stability. †Deceased.

Nanocomposite Derived from Intercalative Spontaneous Polymerization of 2-Ethynylpyridine within Layered Aluminosilicate: Montmorillonite

Intercalation complexes of a conjugated substituted polyacetylene and montmorillonite were prepared through spontaneous polymerization of 2-ethynylpyridine within the galleries of montmorillonite. Protons are thought to be at the origin of spontaneous polymerization of 2-ethynylpyridine. X-ray data support the model of a single inserted polyacetylene layer with the backbone extended “flat” on the lamellar surface and pyridine rings of the repeating unit oriented nearly perpendicular to the surface.

Synthesis and luminescence properties of a poly( p-phenylenevinylene)/montmorillonite layered nanocomposite

A layered nanocomposite of poly( p-phenylenevinylene) (PPV) with montmorillonite clay is prepared at ambient temperature by incorporation of poly( p-xylylenedimethylsulfonium) (PXDMS) into the montmorillonite galleries, followed by the base-mediated elimination of dimethylsulfide. Powder X-ray diffraction on the intermediate and final product show gallery expansions of 5.5 and 4.6 Å, respectively, indicating the nanoscale ordering of polymer and montmorillonite layers. Thermogravimetric analyses of the products indicates the loss of approximately 75% of the sulfonium groups by reaction with base. Luminescence measurements show a shift in emission peak intensities indicating the conversion of PXDMS to PPV within the montmorillonite galleries.