Modified MMT Clay Research Articles

Silk ProteinsEnriched Nanocomposite Hydrogels Based on Modified MMT Clay and Poly(2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropane Sulfonic Acid) Display Favorable Properties for Soft Tissue Engineering.

Due to their remarkable structures and properties, three-dimensional hydrogels and nanostructured clay particles have been extensively studied and have shown a high potential for tissue engineering as solutions for tissue defects. In this study, four types of 2-hydroxyethyl methacrylate/2-acrylamido-2-methylpropane sulfonic acid/montmorillonite (HEMA/AMPSA/MMT) hydrogels enriched with sericin, and fibroin were prepared and studied in the context of regenerative medicine for soft tissue regenerative medicine. Our aim was to obtain crosslinked hydrogel structures using modified montmorillonite clay as a crosslinking agent. In order to improve the in vitro and in vivo biocompatibility, silk proteins were further incorporated within the hydrogel matrix. Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) were performed to prove the chemical structures of the modified MMT and nanocomposite hydrogels. Swelling and rheological measurements showed the good elastic behavior of the hydrogels due to this unique network structure in which modified MMT acts as a crosslinking agent. Hydrogel biocompatibility was assessed by MTT, LDH and LIVE/DEAD assays. The hydrogels were evaluated for their potential to support adipogenesis in vitro and human stem cells isolated from adipose tissue were seeded in them and induced to differentiate. The progress was assessed by evaluation of expression of adipogenic markers (ppar-γ2, perilipin) evaluated by qPCR. The potential of the materials to support tissue regeneration was further evaluated on animal models in vivo. All materials proved to be biocompatible, with better results on the 95% HEMA 5% AMPSA enriched with sericin and fibroin material. This composition promoted a better development of adipogenesis compared to the other compositions studied, due the addition of sericin and fibroin. The results were confirmed in vivo as well, with a better progress of soft tissue regeneration after implantation in mice. Therefore, hydrogel 95% HEMA 5% AMPSA enriched with sericin as well as fibroin showed the best results that recommend it for future soft tissue engineering application.

Fe doped-CoB catalysts with phosphoric acid-activated montmorillonite as support for efficient hydrogen production via NaBH4 hydrolysis

In this study, montmorillonite (MMT) clay was modified with different acids to be used as support material. The modified MMT clay was used to obtain hydrogen in the hydrolysis reactions of NaBH4 (NaBH4-HR) as a support material for the Co–B and Co–Fe–B catalyst. During the activation of MMT clay, the effects of different acids, phosphoric acid (H3PO4) concentration, and impregnation time with H3PO4 were investigated. During the hydrogen generation from the NaBH4-HR, effects of Co loading, Fe loading, NaBH4 concentration, temperature and, catalyst durability were investigated. The maximum HGRs for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B treated with 5 M H3PO4 for 7 days were 1869 and 4536 mL/min/gcatalyst, respectively. The activation energies for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B catalyst samples were 49.5 and 38.90 kJ/mol.

Probing electronic structure of biomineralized hydroxyapatite inside nanoclay galleries

Hydroxyapatite, the most abundant mineral in the human body, is also an important component in design of biomaterials for bone tissue regeneration. Synthetic hydroxyapatite mineralized in the laboratory often does not exhibit the same biological and morphological properties of biogenic hydroxyapatite in human bone. A biomimetic hydroxyapatite structure is synthesized using biomineralization routes inside the clay galleries of montmorillonite clay. Amino acids are used to modify the clay galleries. These amino acids are used to mineralize hydroxyapatite. The molecular interactions between nanoclay, modifiers inside nanoclay (amino acids) and biomineralized hydroxyapatite result in unique morphology, structure and stoichiometry of the biomineralized hydroxyapatite. Prior studies have indicated that this biomineralized hydroxyapatite inside nanoclay galleries is an effective component of tissue engineering bone scaffolds that elicits an optimal biological response from human mesenchymal stem cells. Here, a detailed electron energy-loss spectroscopy (EELS) study is reported that elucidates the differences in hydroxyapatite, biomineralized hydroxyapatite and β-tricalcium phosphate (β-TCP). Comparison of EELS low-loss transitions and energy loss near-edge structure (ELNES) of P-L2,3 edges for these three compounds is done to determine if there are differences in their electronic structures. These changes observed experimentally are compared with prior predictions and simulations using molecular dynamics studies. The simulations predict attractive and repulsive interactions between phosphate, modified MMT clay and aminovaleric acid (amino acid) molecules. Kramers-Kronig analysis is performed on the loss spectra obtained to yield the real and imaginary parts of the dielectric function of the apatites (ε1 and ε 2). We have also used the ε2 spectra obtained to calculate the AC conductivity spectra for the apatites. This study represents a unique experimental probe into molecular interactions in complex biomineralized hydroxyapatite structures. The small changes observed in the energy loss spectra appear to play important biological roles in biomineralized hydroxyapatite such as the ability to differentiate human mesenchymal stem cells into osteoblasts without growth media.

A study of the erosive wear damage on a recycled polymer coating

In this work, erosion tests were carried out to study the wear damage on a coating made of a recycled polymeric matrix (crystal polystyrene) and clay (montmorillonite (MMT)). The latter was modified and purified with bromide quaternary salts (hexadecyltrimethyl ammonium bromide). The coating preparation was by liquid via dissolving 25% crystal polystyrene in a solution of 70% ethyl acetate and 30% acetone, after this, 1wt% of modified MMT clay was added. The clay/polystyrene matrix coating was applied by immersing wood substrates in the liquid phase of the mixture. This process was repeated five times to get the final coating layer on the substrates. An erosion rig similar to that in ASTM G76-95 was used to perform the tests. The abrasive particle used to conduct the erosion tests was glass beads with a particle size between 200 and 240µm. The impact angles were 30°, 45°, 60° and 90° with a velocity of 2.5±0.5m/s. The abrasive flow rate was 5.5±0.5g/min. The room temperature was between 35°C and 40°C. The results showed that the coating presented its maximum erosion rate at 45°. In addition, the erosion rates were decreased in the clay–polystyrene coating compared to those observed in the uncoated specimens at all incident angles. The wear mechanisms identified in SEM images were consistent pitting action, radial cracks and deposition of particle fragments on the coating surfaces.

Copolymerization in dispersion of divinyl benzene–maleic anhydride in the presence of silylated montmorillonite clays

Sodium montmorillonite (NaMMT clay) derivatives were encapsulated in polymer particles obtained through dispersion copolymerization of divinyl benzene (DVB) with maleic anhydride (MA). To evidence the effect of alkyl monoalkoxysilanes upon MMT reaction, a variety of MMT clay functional derivatives were investigated. Particles with an increased size of modified MMT clay dispersed in dichloromethane were obtained using alkyl monoalkoxysilanes with a longer hydrocarbon chain. Relatively long hydrocarbon chains can exhibit a low substitution degree of MMT clay with alkyl monoalkoxysilanes. MMT class with a low substitution degree leads in the presence of alkoxysilanes to particles with average size between 700 and 1200 nm, and when DVB–MA copolymer is added the particles size decreases (~480 nm). The influence of layered silicates on the thermal stability of DVB–MA copolymer as a function of the used vinyl siloxanes derivatives for functionalization of MMT, on one hand, and the nonlinear variation of refractive index of used silanes on the other hand, pointing out the autoassociation during initial reaction of substitution.

Antibacterial activity of poloxamer-modified montmorillonite clay against E. coli

The aim of this study was to understand the antibacterial activity of poloxamer-modified montmorillonite (MMT) clay and to elucidate its possible mechanism. Modified MMT clay was first examined for characterizations of morphology, composition, crystal structure, thermal behavior, and Fourier transform infrared (FTIR) and X-ray photoelectron spectrometry (XPS), exhibiting a weight fraction of approximately 24% of poloxamer, and mainly consisting of Ca, Mg, Al, Si, and O elements in the clay. Pathogenic Gram-negative bacteria, Escherichia coli ( E. coli), were chosen as the antibacterial evaluation indicator of this clay by determining the minimum inhibitory concentration (MIC) in nutrient broth (NB). The amount of cations releasing into NB was also analyzed via inductively coupled plasma mass spectrometry (ICP-MS). Poloxamer-modified MMT clay with a concentration of 2310 ppm was found to depress the growth of E. coli and exhibited a high calcium concentration of approximately 101 ppm releasing into NB. However, it was found that after being used once in the antibacterial test, the modified MMT clay did not retain any antibacterial activity in fresh NB; this is believed to be a result of the loss of poloxamer and decreased numbers of calcium ions incorporated into the used MMT clay, thus lowering bactericide induction, as indicated by the FTIR, XPS and ICP results.

In situ mineralized hydroxyapatite on amino acid modified nanoclays as novel bone biomaterials

A novel biomineralization route to synthesis of hydroxyapatite (HAP) in montmorillonite (MMT) clay galleries modified with 5-aminovaleric acid is presented. The oraganomodified MMT clay with mineralized HAP ( in situ HAPclay) was characterized by transmission Fourier Transform infrared (FTIR) spectroscopy to evaluate molecular interactions between clay-modifier-HAP. FTIR spectroscopy studies indicated the formation of HAP within the modified MMT clay galleries. X-ray diffraction (XRD) studies indicated the formation of apatite in modified MMT clay and also showed shifts in peak positions corresponding to the apatite in in situ HAPclay. This indicated that the apatite formed in in situ HAPclay exhibits differences in its lattice structure as compared to ex situ hydroxyapatite (HAP). The in situ HAPclay was further used for the preparation of nanocomposite chitosan/polygalacturonic acid (ChiPgA) composite films. Human osteoblast cells were cultured on these ChiPgA composite films containing in situ HAPclay. Human osteoblasts form clusters and exhibit good biocompatibility with these films. This work demonstrated the potential to design biomineralized HAP in nanocomposites as new bone biomaterials.

Effect of MMT Clay Content on Thermal Behaviour of MDPE/MMT Nanocomposite

The thermal stability of medium-density polyethylene (MDPE)/Montmorillonite nanocomposite was studied by TGA and DSC methods in a wide range of temperature. The dispersion of the MMT clays on microscopic scales was examined using a Transmission electron microscopy (TEM). The mass loss from thermogravimetric analysis (TGA) was used to study decomposition temperature in a temperature range from room temperature to 800 °C and DSC was used to probe melting and crystallization in a temperature range from room temperature to 300°C. Simultaneous TGA made possible to show that non modified MMT clay and MMT clay modified with alkyl ammonium salt exhibit a significant stabilizing effect on MDPE macromolecules in air atmosphere and DSC shows natural MMT and MMT clay modified with alkyl ammonium salt exhibit a significant change in melting, crystallization, enthalpy and crystalline content of samples. TEM image shows uniform dispersion and intercalation of MMT clays in nanocomposites.

Nanoclay Based Composite Scaffolds for Bone Tissue Engineering Applications

Scaffolds based on chitosan/polygalacturonic acid (ChiPgA) complex containing montmorillonite (MMT) clay modified with 5-aminovaleric acid were prepared using freeze-drying technique. The MMT clay was introduced to improve mechanical properties of the scaffold. The microstructure of the scaffolds containing the modified MMT clay was influenced by the incorporation of nanoclays. The MTT assay also indicated that the number of osteoblast cells in ChiPgA scaffolds containing the modified clay was comparable to ChiPgA scaffolds containing hydroxyapatite known for its osteoconductive properties. Overall, the ChiPgA composite scaffolds were found to be biocompatible. This was also indicated by the scanning electron microscopy images of the ChiPgA composite scaffolds seeded with human osteoblast cells. Photoacoustic–Fourier transform infrared (PA-FTIR) experiments on the ChiPgA composite scaffolds indicated formation of a polyelectrolyte complex between chitosan and polygalacturonic acid. PA-FTIR studies also showed that the MMT clay modified with 5-aminovaleric acid was successfully incorporated in the ChiPgA based scaffolds. Swelling studies on ChiPgA composite scaffolds showed the swelling ability of the scaffolds that indicated that the cells and the nutrients would be able to reach the interior parts of the scaffolds. In addition to this, the ChiPgA scaffolds exhibited porosity greater than 90% as appropriate for scaffolds used in tissue engineering studies. High porosity facilitates the nutrient transport throughout the scaffold and also plays a role in the development of adequate vasculature throughout the scaffold. Compressive mechanical tests on the scaffolds showed that the ChiPgA composite scaffolds had compressive elastic moduli in the range of 4–6 MPa and appear to be affected by the high porosity of the scaffolds. Thus, the ChiPgA composite scaffolds containing MMT clay modified with 5-aminovaleric acid are biocompatible. Also, the ChiPgA scaffolds containing the modified MMT clay appears to satisfy some of the basic requirements of scaffolds for tissue engineering applications.

Use of unnatural amino acids for design of novel organomodified clays as components of nanocomposite biomaterials

Sodium montmorillonite (Na-MMT) clay was modified with three different unnatural amino acids in order to design intercalated clay structures that may be used for bone biomaterials applications. Prior work on polymer-clay nanocomposites (PCNs) has indicated the effect of the appropriate choice of modifiers on enhancing properties of PCNs. Our X-ray diffraction results indicate an increase in the d-spacing of Na-MMT clay after it was modified with the three unnatural amino acids. Transmission Fourier transform infrared spectroscopy experiments were carried out on the unmodified and modified MMT clay samples to study the molecular interactions between the amino acids used as modifiers and the Na-MMT clay. Cell culture experiments showed that the Na-MMT clay modified with the three amino acids was biocompatible as were the modified clay-incorporated films of chitosan/polygalacturonic acid/hydroxyapatite.

Synthesis and characterization of some polyacrylate/montmorillonite nanocomposites by in situ emulsion polymerization using redox initiation system

AbstractIntercalated modification of Montmorillonite clay (MMT) with three different amino acids—Alanine, Leucine, and Phenylalanine—in the presence of hydrochloric acid followed by surface modification by methyl triethoxy silane coupling agent to produce double modified Montmorillonite clay which is characterized by X‐ray diffraction (XRD) and Thermogravimetric analysis (TGA). The data shows an increase in d‐spacing of modified clay as a result of cationic exchange. Double modified MMT clay was used in the preparation of Polyacrylate/clay nanocomposites by using an in situ redox emulsion polymerization of polyglycidylmethacrylate (PGMA) and polymethylmethacrylate (PMMA). The structure and properties of the prepared nanocomposites were achieved by XRD, TGA, and SEM. The results show that all weight loses temperatures for the nanocomposite samples are higher than that of pure polymer in both PGMA and PMMA. It is also obvious that the increasing in the clay content plays an effective role in the increasing of thermal stability of these materials. SEM shows that the clay is more homogenously dispersed in PMMA than in PGMA matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Microsphere pressure sensitive adhesives—acrylic polymer/montmorillonite clay nanocomposite materials

In this study, the synthesis and characterization of acrylic polymer/montmorillonite (MMT) clay nanocomposite pressure sensitive adhesives (PSA) are presented. Different types and amounts of modified and unmodified montmorillonite clays were dispersed in ethyl acrylate (EA)/2-ethylhexyl acrylate (2-EHA) monomer mixture, which was then polymerized using a suspension polymerization technique. Polymerization was monitored in-line using attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy. The adhesion properties of the synthesized nanocomposite materials were determined using standard measurements of tack, peel and shear strength. Viscoelastic properties of dried adhesive films were analyzed using dynamic mechanical analysis (DMA). The results showed that the kinetics of suspension polymerization was independent of the addition of MMT clays. On the other hand, adhesive properties were strongly influenced by the type and the amount of MMT clay added. While peel strength and tack gradually decreased with higher amount of modified MMT clay, a substantial increase in shear strength was determined with a maximal value at 1wt% of added MMT clay. Moderate influence on tack, peel and shear strength was observed when the unmodified type of MMT clay was used. DMA analysis showed an increase in storage modulus (G′) for adhesives synthesized with MMT clay addition, but no significant differences were determined between particular types of MMT clays. A decrease in tanδ value for adhesives with 1wt% of added MMT clay was observed, which also concurs with higher shear strength and implies to the improved cohesion of adhesive.

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.

Synthesis, Fabrication, Characterization, Properties and Thermo-Oxidative Stability Study of Poly(ether imide)/MMT Clay Nanocomposites

A series of partially fluorinated poly(ether imide) (6F-PEI) and (6F-PEI)/Organosoluble MMT clay nanocomposite were synthesized. XRD data, indirectly confirmed the exfoliation of diamine modified MMT clay at molecular level in the nanocomposite. Thermal properties, and longterm thermo-oxidative stability, thermal degradation kinetics, moisture absorption, chemical resistance of (6F-PEI)s, and nanocomposite films were studied and reported in this paper.

Preparation and Characterization of 4,4′‐Bis(4‐aminophenoxy)diphenyl Sulfone Based Fluoropoly(ether‐imide)/Organo‐Modified Clay Nanocomposites

AbstractA series of fluoropoly(ether‐imide) (6F‐PEI), and [6F‐PEI/montmorillonite (MMT) clay) nanocomposites films were made by thermal curing of respective formulations containing fluoropoly(ether‐amic acid) (6F‐PEAA), synthesized from 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4′‐bis(4‐aminophenoxy)diphenyl sulfone (p‐SED), and increasing concentration of p‐SED treated montmorillonite clay (modified MMT clay) at temperature from RT to 350 °C. These films showed excellent solvent resistance as well as very good thermal stability, and increased glass transition (Tg) values with increasing % clay. In addition, these trifluoromethyl groups‐containing nanocomposites films showed sharp lowering of coefficient of thermal expansion (CTE) by 22%. Furthermore, they exhibited increased long‐term thermo‐oxidative stability (TOS), with % weight retention in the range of 86 to 92% in isothermal heating at 300 °C for 300 h in air, reduced water absorption at 100 RH at 50 °C in the range of 0.5 to 1.15%. These data are still much lower than those of neat ULTEM® 1000 and Kapton® H film. The modulus of elasticity is on an average 38% higher for the nanocomposite films relative to neat fluoropoly(ether‐imide) (6FDA + p‐SED), and above non‐fluorinated polyimide films. The surface energy measurement by One‐Liquid and Two‐Liquid method showed a comparable trend of decreasing contact angle. For the nanocomposite films having 15% hydrophobic clay, the contact angle decreased by 21 and 20% for DI‐water and formamide, respectively. The surface energy increase was in the range of 8.21–8.54 mJ/m2.magnified image