Silicate Galleries Research Articles

A research of colloidal silver immobilization in bionanocomposites of natural polymers and montmorillonite

Currently, colloidal silver particles are used in the creation of electronic, optical, and sensor devices of a new generation. Silver-containing bionanocomposites (BNCs) were synthesized by immobilization of colloidal montmorillonite particles containing colloidal silver in a composition of sodium alginate and sodium salt of carboxymethylcellulose. Silver-containing montmorillonite particles Ag-Mt were obtained by replacing Na+ ions in layered silicate galleries with Ag+ ions, followed by the transformation of silver ions into silver particles. The introduction of Ag+ ions into the montmorillonite structure is justified by infrared spectroscopy. When studying the strength of bionanocomposite films, it was found that with an increase in the content of Ag-Mt particles in their composition, the strength increases and the deformation decreases.It is found that the equilibrium values of the swelling constant are set in ~30 minutes. At the same time, with an increase in the Ag-Mt content in the bionanocomposite from 3 % to 10 %, the value of the equilibrium swelling coefficient (Kswell) decreases by 2.8 times. The replacement of Na+ ions with Ag+ ions in the montmorillonite structure is accompanied by a decrease in the swelling of bionanocomposites, which is explained by the lower hydration of Ag+ ions compared to Na+ ions. As another reason for the decrease in the swelling of bimonanocomposites with an increase in the proportion of Ag-Mt in their composition, enhancing their ability to structure formation in the prersence of a clay mineral is indicated.The kinetics of the release of Ag+ ions from bionanocomposites into saline has been studied. It is shown that the release of Ag+ ions increases with increasing pH of the medium

Unusual exfoliation of layered silicate clays by non-aqueous amine diffusion mechanism

The organic ionic exchange intercalation of smectite clays is conventionally performed in water swelling conditions. Here we report a different mechanism for modifying the smectite clays in alcohol solvents. The modification of sodium montmorillonite with poly(oxyethylene-oxypropylene)-amines (POA-amine) were compared for the differences between in water and in alcohol. In water, the intercalation of hydrophobic poly(oxypropylene)-rich amines in the silicate galleries expands the interlayer spacing up to 10 nm and even to exfoliation (featureless in X-ray diffraction pattern) with over 5 amine equivalents, where as hydrophilic poly(oxyethylene)-rich amines could only intercalate in a low spacing of 1.8 nm. On the other hand, all of the POA-amines in isopropanol afford the exfoliation with over, 3 amine equivalents. The mechanism of this unexpected exfoliation is explained by the thermodynamic formations of an imaginary membrane surrounding the clay units, followed by amine diffusion from the solvent into the clay galleries.

Antibiotic-loaded chitosan-Laponite films for local drug delivery by titanium implants: cell proliferation and drug release studies.

In this study, chitosan-Laponite nanocomposite coatings with bone regenerative potential and controlled drug-release capacity are prepared by electrophoretic deposition technique. The controlled release of a glycopeptide drug, i.e. vancomycin, is attained by the intercalation of the polymer and drug macromolecules into silicate galleries. Fourier-transform infrared spectrometry reveals electrostatic interactions between the charged structure of clay and the amine and hydroxyl groups of chitosan and vancomycin, leading to a complex positively-charged system with high electrophoretic mobility. By applying electric field the charged particles are deposited on the surface of titanium foils and uniform chitosan films containing 25-55wt% Laponite and 937-1655µg/cm(2) vancomycin are obtained. Nanocomposite films exhibit improved cell attachment with higher cell viability. Alkaline phosphatase assay reveals enhanced cell proliferation due the gradual dissolution of Laponite particles into the culture medium. In-vitro drug-release studies show lower release rate through a longer period for the nanocomposite compared to pristine chitosan.

Functional copolymer/organo-MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA-alt -1-octadecene)-g -PLA layered silicate nanocomposites with nanoporous core-shell morphology

Novel bioengineering functional copolymer-g-biopolymer-based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L-lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1-octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo-MMT clay (reactive ODA-MMT and non-reactive DMDA-MMT) complexes as nanofillers and tin(oct)2 as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT-IR spectroscopy, X-ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA-DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro- and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H-bonding and self-organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride-containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer-g-biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.

MMT-supported Ag nanoparticles for chitosan nanocomposites: Structural properties and antibacterial activity

Multifunctional bionanocomposites have been prepared by loading chitosan matrix with silver-montmorillonite antimicrobial nanoparticles obtained by replacing Na+ ions of natural montmorillonite with silver ions. This filler has been chosen for its twofold advantage to serve as silver supporting material and to confer new and better performance to the obtained material. It has been proved that the achievement of the intercalation of chitosan into the silicate galleries of montomorillonite as well as the interaction between chitosan and Ag ions and silver particles lead to an enhancement of the thermal stability, to an improvement of mechanical strengths and to a reduction of the liquid water uptake of the obtained bionanocomposites. Results also show that silver ions are released in a steady and prolonged manner providing, after 24 h, a significant reduction in the microbial growth of Pseudomonas spp.

Thermal and Structural Characterization Behavior of Electron Beam Irradiated Rubber/Clay Nanocomposites

ABSTRACTThe effect of electron beam irradiation on the structure, thermal, and morphological properties of ethylene propylene diene monomer (EPDM)/clay and styrene butadiene rubber (SBR)/clay nanocomposites prepared by melt‐blending method has been investigated. The organomodified clay and irradiated rubber/clay samples were characterized using X‐ray diffraction (XRD), energy‐dispersive X‐ray (EDX), and thermogravimetric analysis (TGA). EDX and TGA data confirmed the modification of clay particles using cetyltrimethyl ammonium bromide (CTAB). The XRD patterns of the as‐prepared nanocomposites showed an indication of the presence of exfoliated clay layers at lower clay content whereas a phase‐separated (agglomeration) of organomodified clay layers was present at higher clay content. XRD data of unmodified clay/EPDM composites (EPDM–CCs) indicated that the rubber chains are not intercalated into the silicate galleries, that is, unmodified clay particles are simply incorporated into EPDM matrix in agglomerated states. EPDM–CNs and SBR–CNs nanocomposites show an exfoliated and/or a mixture of intercalated/exfoliated structures at lower (3–5 phr) and higher (10 phr) clay contents, respectively. TGA studies showed that the organomodified clay/rubber nanocomposites show a higher thermal stability in comparison with the unmodified clay/rubber composites. The improvement in the thermal properties is attributed to the organomodification of clay particles as well as the intercalation of rubber chains within silicate layers. In addition, EPDM–CNs nanocomposites exhibit a higher thermal stability than EPDM–CNs nanocomposites. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2014, 33, 21396; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21396

Controlling the growth of polycarbazole within the silicate galleries using peroxides via microwave-assisted green synthesis

The scientific challenges involved in the creation of organic–inorganic hybrid materials based on layered silicates with controlled morphological, optical and electronic properties have evolved considerable interest during the last few decades. The interlayer gap in the Bentonite clay provides an interesting, confined environment for the accommodation of the guest molecule at the nanoscale. Moreover, solid state reactions carried out using the reactants confined in clays, zeolites, silica, alumina or other matrices via microwave irradiation not only produce structures of controlled growth but bring down the handling costs due to simplification of experimental procedure which is important in terms of environmentally benign large scale industrial synthesis. This article highlights for the first time the effect of peroxides in controlling the properties of polycarbazole (PCz) within the Bentonite clay interlayer space in terms of morphology, spectral, and fluorescent properties synthesized through microwave-assisted solid-state intercalation. The orientation of the polymer within such restricted nanoscale environment is expected to be a significant solution for obtaining a better control of the molecular architecture.

Synthesis and characterization of nanoclay–polymer composites from soil clay with respect to their water‐holding capacities and nutrient‐release behavior

ABSTRACTWater and nutrients are two important inputs to agriculture that need to be used judiciously with higher efficiency to save these limited resources. For these purposes, a series of nanoclay–polymer composite (NCPC) superabsorbent nutrient carriers were prepared. These NCPCs were based on the reactions of different types of nanoclays (10 wt %) with partially neutralized acrylic acid and acryl amide by a free‐radical aqueous solution copolymerization reaction with N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator. The nanoclays isolated from three different types of soils were dominant in kaolinite (clay I), mica (clay II), and montmorillonite (clay III), and a portion of each was freed from amorphous aluminosilicate. Thus, there were six different types of nanoclays used, namely, those dominated by kaolinite, mica, and smectite with and without amorphous aluminosilicate. Fourier transform infrared spectroscopy and X‐ray diffraction (XRD) investigations showed evidence of interaction between the clays and polymer. XRD investigation also showed that the reaction between the polymer and clays I and II occurred on the surface of various clay particles without intercalating into the stacked silicate galleries, whereas in the case of clay III (the smectite‐dominated clay), evidence indicated the intercalation of polymer into the stacked silicate galleries of the clay and the exfoliation of the clay. The water absorbency decreased in the NCPCs compared to that of the pure polymeric hydrogel. In case of the pure polymer, the entire amount of nutrient loading released within 15 h of incubation; this was higher than that of the NCPCs. In the initial stage (up to 15 h), no significant differences in nutrient release were observed among the different polymer/clay composites, but there were differences in later stages. Among the different NCPCs, the percentage release of nutrients at 48 h ranged from around 70% in the polymer/clay III composite to 90% in the polymer/clay I composite. The presence of amorphous aluminosilicates in clay did not make any difference in the nutrient‐release rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39951.

Dielectric Properties of Polyaniline-Montmorillonite Clay Hybrids

Polyaniline (PANI)-montmorillonite clay (MMT) hybrid (PANI-MMT) was prepared by mechanical grinding of ANI and MMT in the presence of potassium perdisulphate (KPS) followed by soaking the mass in 0.1 (M) HCI for 24 h. The formation of PANI-MMT hybrid was confirmed by Fourier transform infrared spectroscopic analyses. XRD studies revealed the intercalation of PANI into two-dimensional silicate galleries of MMT HRTEM analyses indicated particle size distribution to be in the range of 40-55 nm. The real part of the dielectric constant reached values as high as 4500 at frequency - 10(2) Hz for a MMT:PANI = 1:1 weight ratio, the value decreasing with increasing frequency up to 25 kHz, and also with increasing MMT loading in the hybrids. This dispersion was indicative of the interfacial space charge polarization (Maxwell Wagner type). Grain boundary resistance and capacitance of the hybrid along with the conductivity-relaxation time for the hybrid at several PANI:MMT weight ratios were evaluated from the complex impedance plot considering the Maxwell-Wagner Two-Layered Model AC conductivity was independent of frequency in the range 0.1-1 kHz and thereafter found to rise in the range 1-25 kHz due to trapped charges. DC conductivity values of the hybrids were lower than the PANI homopolymer.

Synthesis of Poly(cyclohexene oxide)‐Montmorillonite Nanocomposite via In Situ Photoinitiated Cationic Polymerization with Bifunctional Clay

Poly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by means of in situ photoinitiated cationic polymerization with initiator moieties immobilized within the silicate galleries of the clay particles. Diphenyliodonium molecules were intercalated via cation exchange process between Cloisite Ca and diphenyliodonium. The polymerization of CHO through the interlayer galleries of the clay can provide a homogenous distribution of the clay layers in the polymer matrix in nanosize and results in the formation of PCHO/clay nanocomposites. The rates of clay loadings were changed to 1%, 3%, and 5% so as to investigate the effect of clay and initiator amount on polymer. X‐ray diffraction (XRD) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) methods were used for the characterization of modified clay and nanocomposite materials. Thermal stability of PCHO/MMT nanocomposites was also studied by both differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Structure and rheology of nanocomposite hydrogels composed of DNA and clay

The preparation and characterization of the nanocomposite hydrogels based on deoxyribonucleic acid (DNA) and synthetic hectorite (SWN), were reported. Wide-Angle X-ray Diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed that the intercalation of water molecules into the silicate galleries took place and the interaction between PO2- groups of DNA and SWN surfaces. DNA/SWN hydrogels exhibited viscoelastic solid-like properties DNA as revealed by rheological measurements. The stress-relaxation behaviors of DNA/SWN and SWN hydrogels in the linear viscoelastic regime and non-linear viscoelastic regime were examined. The incorporation of DNA macromolecules led to the enhancement of the damping behavior of the dispersed silicate particles as compared with SWN hydrogels without DNA. The softening of the nanocomposite hydrogels was supported by the calculated damping function of the stress-relaxation measurements.

Synthesis and characterization of polysulfone/clay nanocomposite membranes for fuel cell application

AbstractIn the present investigation, polysulfone (PSu) nanocomposites were successfully prepared by solvent casting method. Layered silicates, viz., sodium montmorillonite (NaMMT), Cloisite 93A, and Cloisite 30B were dispersed in PSu to obtain nanocomposite membranes. PSu nanocomposite membranes were tested for mechanical performance, water uptake, thermal properties, X‐ray diffraction, and scanning electron microscopy (SEM). The nanocomposite membranes showed an increment in tensile properties, whereas a reduction was observed in water uptake. X‐ray diffraction studies confirmed the intercalation of PSu within the silicate galleries. SEM analysis confirmed an increase in the porosity of the membrane with the incorporation of nanoclays. Thermo gravimetric analysis (TGA) thermograms indicated an increase in the thermal stability of PSu nanocomposites. Evaluation of conductivity characteristics and single cell performance revealed improved output for organomodified clay nanocomposites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Nanocomposites with Biodegradable Polycaprolactone Matrix

AbstractSummary: Biodegradable polymer/clay nanocomposites and/or composites based on poly(ε‐polycaprolactone) (PCL) were prepared by conventional melt mixing. Three kinds of clays, organomodified Cloisite 15A and Cloisite 10A with different ammonium cations located in the silicate gallery and unmodified Cloisite with Na cations were used for composites preparation. The degree of dispersion of silicate layers in the matrix was determined by X‐ray diffraction and transmission electron microscopy. Oscillatory rheological measurements were used for characterization of the physical network formed by the filler. The presence of intercalated and exfoliated structures were observed for the composites PCL/Cloisite 15A and PCL/Cloisite 10A, indicating that nanocomposite structure was formed. Changes of viscoelastic properties to more solid‐like behavior, especially in the low frequency range were explained by formation of silicate network structure, which can be detected by modified Cole‐Cole plots.

Preparation and characterization of poly(methyl methacrylate)–clay nanocomposites via melt intercalation: Effect of organoclay on thermal, mechanical and flammability properties

The PMMA nanocomposites were prepared by melt processing method. The influence of organoclay loading on extent of intercalation, thermal, mechanical and flammability properties of poly(methyl methacrylate) (PMMA)–clay nanocomposites were studied. Three different organoclay modifiers with varying hydrophobicity (single tallow vs. ditallow) were investigated. The nanocomposites were characterized by using wide angle X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. The intercalation of polymer chain within the silicate galleries was confirmed by WAXD and TEM. Mechanical properties such as tensile modulus ( E), tensile strength, percentage elongation at break and impact strength were determined for nanocomposites at various clay loadings. Overall thermal stability of nanocomposites increased by 16–17 °C. The enhancement in T g of nanocomposite is merely by 2–4 °C. The incorporation of maleic anhydride as compatibilizer further enhanced all the properties indicating improved interface between PMMA and clay. The flammability characteristics were studied by determining the rate of burning and LOI.

Preparation, characterization, and properties of sodium montmorillonite clay/poly(styrene–butadiene–styrene) containing quaternary ammonium cations and photoinitiator nanocomposites via ultraviolet exposure

AbstractA functionalized graft copolymer {poly(styrene–butadiene–styrene) (SBS)‐g‐4‐benzoyl‐N,N‐dimethyl‐N‐[2‐(2‐methyl‐1‐oxo‐2‐propenyloxy)ethyl]benzenemethanaminium bromide (4‐BBPDMAEMA)}, containing a photoinitiator, quaternary ammonium cations, and many CC double bonds, was synthesized to modify clays, such as Na+–montmorillonite (MMT) clay, for the preparation of organic–inorganic nanocomposite resins via radical photoinduced crosslinking polymerization. The structure of SBS‐g‐4‐BBPDMAEMA was characterized by Fourier transform infrared and 1H‐NMR spectroscopy. The corresponding SBS‐g‐4‐BBPDMAEMA was found to have two functions: the capability to ionically exchange with sodium ions in the silicate gallery and the capability to synthesize exfoliated SBS/MMT nanocomposites by the UV crosslinking of intercalation polymerization. The results from the X‐ray diffraction primarily reveal that the clay platelets should have been exfoliated or completely disordered. However, the results from transmission electron microcopy confirmed that a mixture of partially exfoliated and intercalated structures presented in the nanocomposites. Dynamic mechanical thermal analysis testing indicated that the glass‐transition temperature of the polybutadiene phase and polystyrene phase moved to a lower temperature. Data of thermogravimetric analysis and testing of the mechanical properties showed that the thermal stability and mechanical properties of SBS‐g‐4‐BBPDMAEMA could be regulated by the crosslinking and content of MMT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Study of the combined effect of both clay and glycerol plasticizer on the properties of chitosan films

Chitosan-based nanocomposites at different sodium montmorillonite loadings, with and without glycerol as plasticizer, were produced by solution casting. The combined effect of glycerol and silicate clay on the thermal, mechanical and barrier properties of the obtained nanocomposites was investigated. Films containing 10% (wt/wt) of Na-MMT show, with respect to neat chitosan, reduced water permeability of about 30% and 50% and an increased tensile strength of about 120% and 25%, for films with and without glycerol, respectively. The improvement of barrier and mechanical properties was correlated both to the films nanostructure and to the interactions between chitosan, Na-MMT and glycerol. XRD results suggest that in films without glycerol, which exhibit the best barrier properties, the Na-MMT stacks lay with their platelets parallel to the casting surface. The nanocomposites obtained with addition of glycerol show the best mechanical properties due to the enhancement of chitosan intercalation in the silicate galleries.

Study on the Polyvinylalcohol/Montmorillonite Composite Hydrogel

A series of alkyl ammonium/montmorillonite (MMT) were compounded with polyvinyl alcohol (PVA) to prepare the composite hydrogel with improved water absorbency and mechanical property. The effect of the nature of the surfactants on the intercalation of PVA chains within the silicate galleries, the interfacial compatibility and the properties of the composites was studied. A proper type and content of MMT can increase the glass transition temperature, and enhance the swelling behavior and the mechanical properties of the composites. In order to investigate the interaction of the molecules of PVA with water, the state of water in the hydrogel was studied.

Advanced compounding: Extrusion of polypropylene nanocomposites using the melt pump

A melt pump was assembled into the compounding line to ensure both sufficient time for diffusion process of polymer chains into the silicate gallery and sufficient mechanical shear energy for exfoliation of clay layers. The melt pump in front of the open co-rotating twin-screw extruder controls the throughput rate and the residence time, whereas the screw speed and screw geometry in the extruder determine the mechanical shear energy applied on the compound. Due to melt pump employment, the melt in metering zone can be accumulated, which results in higher mixing efficiency. It was found that using the melt pump leads to up to two times higher residence time and, consequently, higher level of material reinforcement as investigated by extensional rheology. Different melt pump adjustments, screw geometries, and screw speeds were tested and their effect on processing characteristics and material reinforcement was investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Poly(styrene‐b‐tetrahydrofuran)/clay nanocomposites by mechanistic transformation

AbstractSynthesis of poly(styrene‐block‐tetrahydrofuran) (PSt‐b‐PTHF) block copolymer on the surfaces of intercalated and exfoliated silicate (clay) layers by mechanistic transformation was described. First, the polystyrene/montmorillonite (PSt/MMT) nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. Transmission electron microscopy (TEM) analysis showed the existence of both intercalated and exfoliated structures in the nanocomposite. Then, the PSt‐b‐PTHF/MMT nanocomposite was prepared by mechanistic transformation from ATRP to cationic ring opening polymerization (CROP). The TGA thermogram of the PSt‐b‐PTHF/MMT nanocomposite has two decomposition stages corresponding to PTHF and PSt segments. All nanocomposites exhibit enhanced thermal stabilities compared with the virgin polymer segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2190–2197, 2009

Synthesis of Polybutadiene Nanocomposites: In situ Polymerization of 1,3‐Butadiene Catalyzed by Phyllosilicate Interlayer Spacing‐Confined Cobalt(II) Phosphine Complexes

AbstractHeterogeneous phyllosilicate interlayer spacing‐confined cobalt catalysts were prepared by reaction of cobalt phosphine complexes with methylaluminoxane‐modified clay. The catalytic systems obtained were used for the in situ polymerization of 1,3‐butadiene. The polymerization taking place within the silicate galleries separates the pristine layer aggregates, allowing for the design of polybutadiene‐based nanocomposites through the intercalation of the active polymerization centers. Depending on the type of cobalt complex used (i.e., type of phosphine bond to the metal) it is possible to control the microstructure (1,2 content) and the tacticity (percentage of rr, mr and mm triads) of the polymer growing directly in between the inorganic silicate host lamellae.magnified image