Self-assembly behavior of polymer-assisted clays

Montmorillonite Exfoliation in LLDPE and Factors Affecting Its Orientation: From Monolayer to Multi-Nano-Layer Polymer Films

The motivations of the present work are to investigate the exfoliation of montmorillonite within a linear low-density polyethylene matrix and to control its orientation during the cast extrusion process. The first part is focused on the exfoliation of the montmorillonite through the melt extrusion process. The accuracy and relevance of each method used to determine the exfoliation state of montmorillonite have been examined, thanks to X-ray diffraction, transmission electronic microscopy, and rheology. All these methods have presented limitations, but the combination of all leads to a better estimation of the exfoliation state. Finally, the orientation of the montmorillonite is quantified systematically by X-ray texture analysis and correlated with process parameters to discern which one is affecting their orientation. The results have demonstrated an enhancement of the "in-plane" orientation of the montmorillonite with the exfoliation, especially at high concentration and when combined with cast extrusion. Finally, in the multi-nano-layer polymer film configuration, the reduction of the individual layers 29 nm thickness leads to some orientation improvements. However, these improvements are almost at the same level as the concentration effect in a monolayer system. This work gives an overview of all the parameters needed to achieve a significant organo-modified montmorillonite "in-plane" orientation.

Photocurable Carbon Nanotube/Polymer Nanocomposite for the 3D Printing of Flexible Capacitive Pressure Sensors

A photocurable resin/carbon nanotube (CNT) nanocomposite was fabricated from aligned CNTs in an acrylic matrix. The conductivity of the nanocomposite increased rapidly and then stabilized when the CNT content was increased up to and beyond the percolation threshold. Various structures were created using a digital light processing (DLP) 3D printer. Various polymeric dispersants (SMA-amide) were designed and synthesized to improve the CNT dispersion and prevent aggregation. The benzene rings and lone electron pairs on the dispersant interacted with aromatic groups on the CNTs, causing the former to wrap around the latter. This created steric hindrance, thereby stabilizing and dispersing the CNTs in the solvent. CNT/polymer nanocomposites were created by combining the dispersant, CNTs, and a photocurable resin. The CNT content of the nanocomposite and the 3D printing parameters were tuned to optimize the conductivity and printing quality. A touch-based human interface device (HID) that utilizes the intrinsic conductivity of the nanocomposite and reliably detects touch signals was fabricated, enabling the free design of sensors of various styles and shapes using a low-cost 3D printer. The production of sensors without complex circuitry was achieved, enabling novel innovations.

Regulating Chemistry Composition on a Crystal Surface by Introducing a Cation Trapping Agent: A Novel Strategy to Tune Moisture Sensitivity of Crystals

The crystal moisture sensitivity can be tuned by the chemical composition on the crystal surface. Ammonium dinitramide (ADN) crystal is a promising oxidizer for solid propellants. However, its strong moisture sensitivity greatly limits its practical applications. Here, we report a novel strategy to reduce moisture sensitivity by trapping ammonium cations with montmorillonite (MMT) to modulate the chemistry composition on the ADN crystal surface. An extraordinary phenomenon can be found: the crystal surface of the recrystallized ADN with 1% MMT (ADN-1% MMT) is rearranged with more low-surface-energy -NO₂ groups (65.84%) and less high-surface-energy NH₄⁺ groups (4.8%). In addition, ADN-1% MMT presents a more homogeneous low surface energy feature with a narrower surface energy distribution. As a result, ADN-1% MMT exhibits a noticeably lower hygroscopicity at 20 °C and 60% RH, which is accordant with the simulated hygroscopicity based on XRD and moisture sensitivity prediction based on surface energy. This study brings out a novel modification idea to adjust crystal moisture sensitivity by tuning the chemistry composition on the crystal surface based on trapping cations.

Triangular gold nanoplates/two-dimensional nano mica platelets with a 3D lightning-rod effect as flexible nanohybrid substrates for SERS bacterial detection

Triangular gold nanoplates (TAuNPs) were prepared by a one-step rapid growth method and then reduced and stabilized on two-dimensional nano mica nanoplatelets (NMPs). We also prepared TAuNP/NMP nanohybrids with a three-dimensional lightning-rod effect by oxidative etching. The surface of the delaminated NMPs (only 1 nm thick) is highly charged and can provide a large specific surface area; thus, it can be used as a substrate for the stable growth of gold nanoplates. In addition, by controlling relevant synthesis parameters, the edge length of the TAuNPs can be easily adjusted in the range of 30-90 nm. During reduction of the TAuNPs, the cationic surfactant cetyltrimethylammonium chloride was added as a protective agent to surround the TAuNPs; consequently, the surface was positively charged, which facilitates adsorption for detecting molecules with negative charges. When nanohybrids were used in surface-enhanced Raman spectroscopy (SERS) to detect adenine molecules, the limit of detection concentration was 10^-9 M. The Raman enhancement factor was 5.7 × 10⁷, and the relative standard deviation (RSD) was 9.8%. Finally, this method was applied to the biological detection of Staphylococcus aureus, and the surface charge and hydrophilic properties of the material significantly improved the SERS signal of S. aureus. The limit of detection concentration was 10² CFU mL^-1, and the RSD was 11.2%. The TAuNP/NMP nanohybrids can provide very rapid and sensitive SERS detection of biomolecules.

Hydrophilic-Hydrophobic Nanohybrids of AuNP-Immobilized Two-Dimensional Nanomica Platelets as Flexible Substrates for High-Efficiency and High-Selectivity Surface-Enhanced Raman Scattering Microbe Detection

A flexible hybrid substrate was developed by affixing gold nanoparticles (AuNPs) onto the surface of two-dimensional nanomica platelets (NMPs). The substrate was successfully used in biosensors with high efficiency and high selectivity through surface-enhanced Raman scattering (SERS). By controlling the amphiphilicity of the hybrid substrate, the flexible substrate was made highly selective toward biomolecules. Four different SERS substrate systems were constructed, including intercalated mica, exfoliated NMPs, hydrophilic exfoliated NMPs, and hydrophobic exfoliated NMPs. NMPs were only 1 nm thick. AuNPs adsorbed on both sides of NMPs and thus created excellent three-dimensional hot junction effects in the z-axis direction. For the detection of adenine in DNA, a satisfactory Raman enhancement factor (EF) of up to 8.9 × 10⁶ was achieved with the detection limit as low as 10^-8 M. Subsequently, the AuNP/NMP hybrids were adopted to rapidly detect hydrophilic Staphylococcus hominis and hydrophobic Escherichia coli. The AuNP/PIB-POE-PIB/NMP nanohybrid was concurrently hydrophilic and hydrophobic. This amphiphilic property greatly enhanced the detection selectivity and signal intensity for hydrophilic or hydrophobic bacteria. Overall, AuNPs/PIB-POE-PIB/NMPs developed as SERS substrates enable rapid, sensitive biodetection.

Bioapplication of cyclodextrin-containing montmorillonite

Recent progresses in the integration of CDs and montmorillonite, as well as applications of CD-containing montmorillonite hybrid host systems are summarized in this review. Several efficient synthesis strategies, such as ion exchange, metal coordination, supramolecular strategies, polymerizations and organic synthesis methods, have been discussed during the preparation of CDs/montmorillonite hybrid composites. In particular, diverse instrumental techniques were highly recommended for characterizing the as-obtained hybrid systems, including their chemical composition and structures, crystallinity, surface/self-assembled morphologies, as well as other particular physiochemical properties, providing a direct guide for promoting the desired structures and exploring various applications. It should be noted that the introduction of functional groups, as well as the integration of CDs and montmorillonite granted the thus obtained CD-containing montmorillonite hybrid host systems a lot of unique features, providing great opportunities for expanding the practical applications to a series of biological and environmental areas, such as biosensors, sorption and decontamination of bio/environmental hazardous materials, biostudies about aqueous dispersity, stability and biocompatibility, drug loading and target delivery, controlled and sustained drug release, as well as antibacterial.

Energetics, Interlayer Molecular Structures, and Hydration Mechanisms of Dimethyl Sulfoxide (DMSO)-Kaolinite Nanoclay Guest-Host Interactions

Two-dimensional (2D) kaolinite nanoclay is an important natural mineral with promising application potential, especially tuned with organic intercalates. However, thus far, the organics-kaolinite guest-host interactions, the atomic scale structures of organic intercalates under confinement, and molecular level mechanisms of hydration are rarely systematically explored using both experimental and computational methodologies. We integrated density functional theory with dispersion scheme (DFT-D) with various experimental methods to investigate the intercalation of dimethyl sulfoxide (DMSO) in kaolinite with and without hydration. The kinetic, thermodynamic, and structural impacts of hydration were highlighted. In short, water molecules significantly promote intercalation of DMSO into kaolinite because of favorable intercalation energy, which is enabled by effective hydrogen bonding at the guest species (DMSO and water)-kaolinite interfaces.

Effect of Polymer Length on the Adsorption onto Aluminogermanate Imogolite Nanotubes

This study evidences the adsorption of model nonionic polymers onto aluminogermanate imogolite nanotubes, attractive porous nanofillers with potential molecular loading and release applications. We resolve the underlying mechanisms between nanotubes and polyethylene glycols with different molecular weights by means of nanoisothermal titration calorimetry. The analysis of the results provides a direct thermodynamic characterization, allowing us to propose a detailed description of the energetics involved in the formation of polymer/imogolite complexes. The affinity toward the nanotube surface is enthalpy-driven and strongly depends on the polymer chain length, which significantly affects the polymer configuration and the flow properties of the resulting complexes, probed by small-angle neutron scattering and rheology, respectively. These findings open new avenues for the rational design of these hybrid mixtures for advanced applications.

High Elongation and Transparent Nacre-Inspired PVA/MMT Nanocomposites

Currently, high strength nacre-inspired PVA/MMT (polyvinyl alcohol/montmorillonite) nanocomposites with high MMT nanofiller content (50-70 wt%) have been constructed successfully. However, this seriously sacrifices the elongation and reduces the corresponding transparency. In this paper, high elongation and transparent PVA/MMT nanocomposites with high MMT content are prepared by the evaporation-induced assembly with the introduction of the micro-crosslinking. Results demonstrate that the micro-crosslinking can inhibit the formation of rod-shaped arrays, and contribute to a more ordered layered microstructure, where an elongation of 76.2% in 47.8 wt% MMT content nanocomposites is gained, nearly 19 times of that of non-crosslinked nanocomposites (ultimate strain is 4.1%). This provides a potential approach for compromise between high strength and excellent elongation at the same MMT content. Moreover, disappearance of rod-shaped arrays and resultant ordered layered microstructure make eventual films more transparent.

Supramolecular dendrimer-containing layer-by-layer nanoassemblies for bioapplications: current status and future prospects

This review provides a comprehensive and critical overview of the supramolecular dendrimer-containing multifunctional layer-by-layer nanoassemblies driven by a multitude of intermolecular interactions for biological and biomedical applications.

Bio-Inspired Preparation of Clay-Hexacyanoferrate Composite Hydrogels as Super Adsorbents for Cs. ACS APPLIED MATERIALS & INTERFACES 2020;12:33173-33185. [PMID: 32531151 DOI: 10.1021/acsami.0c06598]

A facile and low-cost fabrication route, inspired by the adhesive proteins secreted by mussels, has been developed to prepare a clay-based composite hydrogel (DHG(Cu)) containing hexacyanoferrate (HCF) nanoparticles for the selective removal of Cs⁺ from contaminated water. Initially, montmorillonite was exfoliated prior to coating with a thin layer of polydopamine (PDOPA) via the self-polymerization of dopamine. Mixing the composite (D-clay) with the HCF precursor, followed by the addition of copper ions, led to the self-assembly of the polymer-coated exfoliated clay nanosheets into a three-dimensional network and in situ growth of KCuHCF nanoparticles embedded within the gel structure. Analytical characterization verified the fabrication route and KCuHCF immobilization by a copper-ligand complexation. Rheology testing revealed the composite hydrogel to be elastic under low strain and exhibited reversible, self-healing behavior following high strain deformation, providing a good retention of KCuHCF nanoparticles in the membrane. The adsorbent DHG(Cu) showed a superior Cs⁺ adsorption capacity (∼173 mg/g), with the performance maintained over a wide pH range, and an excellent selectivity for Cs⁺ when dispersed in seawater at low concentrations of 0.2 ppm. On the basis of its excellent mechanico-chemical properties, the fabricated hydrogel was tested as a membrane in column filtration, showing excellent removal of Cs⁺ from Milli-Q water and seawater, with the performance only limited by the fluid residence time. For comparison, the study also considered other composite hydrogels, which were fabricated as intermediates of DHG(Cu) or fabricated with Fe³⁺ as the cross-linker and reactant for HCF nanoparticle synthesis.

Transparent Polyimide/Organoclay Nanocomposite Films Containing Different Diamine Monomers

Poly (amic acid) s (PAAs) were synthesized using 4,4′-(hexafluoroisopropyl-idene) diphthalic anhydride (6FDA) and two types of diamines—bis(3-aminophenyl) sulfone (BAS) and bis(3-amino-4-hydroxyphenyl) sulfone (BAS-OH). Two series of transparent polyimide (PI) hybrid films were synthesized by solution intercalation polymerization and thermal imidization using various concentrations (from 0 to 1 wt%) of organically modified clay Cloisite 30B in PAA solution. The thermo-mechanical properties, morphology, and optical transparency of the hybrid films were observed. The transmission electronic microscopy (TEM) results showed that some of the clays were agglomerated, but most of them showed dispersed nanoscale clay. The effects of -OH groups on the properties of the two PI hybrids synthesized using BAS and BAS-OH monomers were compared. The BAS PI hybrids were superior to the BAS-OH PI hybrids in terms of thermal stability and optical transparency, but the BAS-OH PI hybrids exhibited higher glass transition temperatures (T_g) and mechanical properties. Analysis of the thermal properties and tensile strength showed that the highest critical concentration of organoclay was 0.50 wt%.

Facile Fabrication of Flexible Electrodes and Immobilization of Silver Nanoparticles on Nanoscale Silicate Platelets to Form Highly Conductive Nanohybrid Films for Wearable Electronic Devices

This study investigated films with remarkably high electrical conductivity after they were easily prepared from organic/inorganic nanohybrid solutions containing an organic polymeric dispersant and two-dimensional nanoscale silicate platelets as the inorganic stabilizer dispersed with silver nanoparticles. Transmission electron microscopy shows that the production of silver nanoparticles synthesized by the in situ chemical reduction of AgNO₃ in an aqueous solution by N,N-dimethylformamide results in an average silver nanoparticle diameter of circa 20 nm. Thin films of silver nanoparticles were prepared on a 1-μm-thick film with a low sheet resistance of 8.24 × 10^-4 Ω/sq, achieved through the surface migration of silver nanoparticles and prepared by sintering at 300 °C to form an interconnected network. This was achieved with a silver nanoparticle content of 5 wt%, using nanoscale silicate platelets/polyoxyethylene-segmented polyimide/AgNO₃ at a weight ratio of 1:10:35. During sintering, the color of the hybrid film changed from gold to milky white, suggesting the migration of silver nanoparticles and the formation of an interconnected network. The results show promise for the fabrication of novel silver-based electrocardiogram electrodes and a flexible wireless electrocardiogram measurement system for wearable electronics.

Multifunctional films with a highly oriented "nano-brick wall" structure by regulating modified TiO2@graphene oxide/poly(vinyl alcohol) nanocomposites

High-performance packaging materials featuring a superior gas barrier and UV resistance as well as excellent mechanical properties are highly desirable but are still encountering serious challenges in the food, pharmaceutical and electronic industries. Here, a multifunctional film based on a modified titanium dioxide@graphene oxide/poly(vinyl alcohol) (TiO2@GO/PVA) nanocomposite with a multilayer nano-brick wall structure is rationally designed and fabricated by a facile solution casting approach. The modified TiO2 nanoparticles, assembled on the surface and edges of GO, are employed as bridges to construct the GO edge-to-edge alignment. Then, they tightly combine with PVA chains, acting as the mortar, to form a multilayer compact film. Therefore, the oxygen permeability of the nanocomposite film decreases to 0.119 × 10-17 cm3·cm (cm2·s·Pa)-1 with the addition of 1.0 wt% GO and 1.2 wt% modified TiO2, reduced by 93% compared with pure PVA film. More impressively, it is increased by only 5.9% after 9 h of ultraviolet light irradiation, which shows its exceptional UV resistance ability. In addition, the mechanical performance, thermal stability and water resistance are substantially improved. The developed modified TiO2@GO/PVA nanocomposite films with outstanding performance can be perceived as a green biodegradable material for a wide range of packaging industries.

Immobilization and 3D Hot-Junction Formation of Gold Nanoparticles on Two-Dimensional Silicate Nanoplatelets as Substrates for High-Efficiency Surface-Enhanced Raman Scattering Detection

We synthesize a high-efficiency substrate for surface-enhanced Raman scattering (SERS) measurements, which is composed of gold nanoparticles (AuNPs) on two-dimensional silicate nanoplatelets acting as an inorganic stabilizer, via the in-situ reduction of hydrogen tetrachloroaurate (III) by sodium citrate in an aqueous solution. Silicate platelets of ~1-nm thickness and various sizes, viz. laponite (50 nm), sodium montmorillonite (Na⁺⁻MMT, 100 nm), and mica (500 nm), are used to stabilize the AuNPs (Au@silicate), which are formed with uniform diameters ranging between 25 and 30 nm as confirmed by transmission electron microscopy (TEM). In particular, the laponite SERS substrate can be used in biological, environmental, and food safety applications to measure small molecules such as DNA (adenine molecule), dye (Direct Blue), and herbicide (paraquat) as it shows high detection sensitivity with a detection limit of 10-9 M for adenine detection. These highly sensitive SERS substrates, with their three-dimensional hot-junctions formed with AuNPs and two-dimensional silicate nanoplatelets, allow the highly efficient detection of organic molecules. Therefore, these Au@silicate nanohybrid substrates have great potential in biosensor technology because of their environmentally-friendly and simple fabrication process, high efficiency, and the possibility of rapid detection.

Sustained antibacterial activity of berberine hydrochloride loaded supramolecular organoclay networks with hydrogen-bonding junctions

The environmental risk from antibiotics is an issue of increasing concern. So, carboxymethyl β-cyclodextrin-functionalized montmorillonite nanosheets were for the first time successfully synthesized through a cheap, environmentally friendly and scalable approach and confirmed by FTIR, XRD and TGA. FE-SEM investigation showed that the resulting functional material could be further self-assembled into dense supramolecular organoclay networks (D-networks). The antibacterial properties of the D-networks loaded with natural berberine hydrochloride (BBH) were investigated toward E. coli and S. aureus by using colony growth on agar plates, bacterial growth curves based on optical densities, and confocal and fluorescence microscopy. Our studies demonstrated that the BBH loaded D-network antibacterial activity was concentration dependent and significantly exceeded that of free BBH. FE-SEM observation confirmed that E. coli and S. aureus can directly contact the D-networks and confocal and fluorescence microscopy showed that free BBH was only very poorly internalized, while the BBH released from the BBH-loaded D-network could be internalized efficiently into bacterial cells, resulting in an increment of the intracellular BBH level compared with the free BBH group. Time-dependent antibacterial activity was observed and it was found that the BBH-loaded D-network dispersion at the BBH dosage of 600 μg mL^-1 almost completely suppressed the growth of E. coli, leading to a viability loss of up to 98.45 ± 1.22%, while the BBH-loaded D-network dispersion at the BBH concentration of 250 μg mL^-1 exhibited a growth inhibition of 97.81 ± 0.83% toward S. aureus over three days. Our results suggest that supramolecular organoclay networks, in the future, may function as promising antibacterial drug carrier systems to promote BBH delivery in E. coli and S. aureus, which can reduce the environmental risk of antibiotics.

Patterning of Nanoclays on Positively Charged Self-Assembled Monolayers via Micromolding in Capillaries

Nanoclays are nanomaterials with versatile adsorptive properties. This contribution describes the generation of micropatterns of a nanoclay ("laponite") on ammonium-terminated, self-assembled monolayers (SAMs) on glass and silicon. Microstructured immobilization of the laponite was performed using micromolding in capillaries (MIMIC). The immobilization was verified using contact angle goniometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and fluorescence microscopy. Furthermore, laponite was modified with Nile red to generate a fluorescence enhancement-based surface sensor for the vitamin choline.

Organo-clay hybrid hydrophobic spherical styrene divinylbenzene crosslink beads for high-performance carbon dioxide capture

Synthesis of industrially most valuable and low-cost materials for repeated CO₂ adsorption at low temperatures and desorption without energy.

Recyclability of organically modified clays for oil absorption and recovery

The ODA modified organoclay could be used as a crude oil absorbent with high recyclability and stable reusability.

Aggregation of layered double hydroxide nanoparticles in the presence of heparin: towards highly stable delivery systems

Heparin coating significantly enhanced the colloidal stability of layered double hydroxide nanoparticles.

Pancreatic cancer therapy using an injectable nanobiohybrid hydrogel

Nanobiohybrid hydrogels, composed of biocompatible inorganic nanoparticles and biodegradable polymeric hydrogels, have been developed as the sustained delivery carrier of gemcitabine for the treatment of pancreatic cancer.

Immobilization of silver nanoparticles on exfoliated mica nanosheets to form highly conductive nanohybrid films

Highly electrically conductive films were prepared by coating organic/inorganic nanohybrid solutions with a polymeric dispersant and exfoliated mica nanosheets (Mica) on which silver nanoparticles (AgNPs) had been dispersed in various components. Transmission electronic microscopy showed that the synthesized AgNPs had a narrow size distribution and a diameter of approximately 20 nm. Furthermore, a 60 μm thick film with a sheet resistance as low as 4.5 × 10(-2) Ω/sq could be prepared by controlling the heating temperature and by using AgNPs/POE-imide/Mica in a weight ratio of 20:20:1. During the heating process, the surface color of the hybrid film changed from dark golden to white, suggesting the accumulation of the AgNPs through surface migration and their melting to form an interconnected network. These nanohybrid films have potential for use in various electrically conductive devices.

Fabrication of Epoxy Vesicles using Self-Assembling Polystyrene-Montmorillonite Nanocomposite Reusable Template

We report the fabrication of thermoset vesicles using a thermoplastic-clay nanocomposite vesicle reusable template. Epoxy polymer vesicles (EPV) of micrometer diameters were synthesized from bisphenol-A diglycidyl ether resin encapsulated within a self-assembled, polystyrene-montmorillonite hybrid nanocomposite (PCN) template and in situ cross-linked with polyamine curing agent. The size and wall thickness of the EPV vesicles were shown to be controlled by the epoxy resin concentration up to a critical epoxy concentration of 20 wt %, beyond which the wall thickness alone was found to be increasing. The EPVs dispersed in a polystyrene matrix at a loading of 2 wt % were found to reduce the dielectric constant of polystyrene from 3.1 to 2.0, and a linear decrease with decreasing wall thickness of the EPV, attributed to the increase in free volume involving the intrinsic porosity from the rigid epoxy vesicles and the composite, exhibited improved thermal stability also. The result suggests that vesicles produced by micromolding using self-assembled PCN can be utilized for the synthesis of polymer microcomposites having good interfacial bonding as well as low dielectric constant and good thermal stability for use in electronic packaging applications.

Synergy between polyaniline and OMt clay mineral in Langmuir-Blodgett films for the simultaneous detection of traces of metal ions

We report on Langmuir-Blodgett (LB) films made with emeraldine salt polyaniline (PAni-ES) and organophilic montmorillonite clay mineral (OMt), where synergy between the components was reached to yield an enhanced performance in detecting trace levels of cadmium (Cd(2+)), lead (Pb(2+)) and copper (Cu(2+)). Detection was carried out using square wave anodic stripping (SWAS) voltammetry with indium tin oxide (ITO) electrodes modified with LB films of PAni-ES/OMt nanocomposite, whose data were compared to those obtained with electrodes coated with neat PAni-ES and neat OMt LB films. The enhanced performance in the nanocomposite may be attributed to the stabilizing and ordering effect promoted by OMt in PAni-ES Langmuir films, which then led to more homogeneous LB films. According to X-ray diffraction data, the stacking of OMt layers was preserved in the LB films and therefore the PAni-ES chains did not cause clay mineral exfoliation. Instead, OMt affected the polaronic state of PAni-ES as indicated in UV-vis, Raman and FTIR spectra, also consistent with the changes observed for the Langmuir films. Taken together these results do indicate that semiconducting polymers and clay minerals may be combined for enhancing the electrical properties of nanostructures for sensing and related applications.

Enhanced thermal stability and lifetime of epoxy nanocomposites using covalently functionalized clay: experimental and modelling

Relationship between thermal degradation model of epoxy nanocomposites containing different types of modified nanoclay and their structural changes is explained.

Novel chitosan-based/montmorillonite/palladium hybrid microspheres as heterogeneous catalyst for Sonogashira reactions

The objective of this study was to develop novel chitosan-based/montmorillonite/palladium (CS/MMT/Pd) hybrid microsphere catalysts with improved properties for use in Sonogashira reactions.

Temperature-dependent oil absorption of poly(oxypropylene)amine-intercalated clays for environmental remediation

Highly efficient absorption of crude oil by organoclays, which clearly separate from water via LCAT.

Bi-axially oriented polystyrene/montmorillonite nanocomposite films

Polystyrene (PS)/montmorillonite (MMT) nanocomposite films were prepared by bi-axially stretching compounded and extruded PS/MMT nanocomposite sheets, resulting in an improved level of exfoliation and orientation during stretching.

Supramolecular assemblies constructed from β-cyclodextrin-modified montmorillonite nanosheets as carriers for 5-fluorouracil

5-Fluorouracil-loaded supramolecular assemblies formed from self-assembling β-cyclodextrin modified montmorillonite nanosheets exhibit better antitumor activity and lower cytotoxicity in vitro.

Dendrimer-like assemblies based on organoclays as multi-host system for sustained drug delivery

Chemical modification of nanoclay will ensure further progress on these materials. In this work, we show that montmorillonite (MTM) nanosheets can be modified with β-cyclodextrin (CD) via a nucleophilic substitution reaction between mono-6-(p-toluenesulfonyl)-6-deoxy-β-CD and an amino group of 3-aminopropyltriethoxysilane (APTES)-functionalized MTM. The resulting MTM-APTES-CD can be further self-assembled into dendrimer-like assemblies, exhibit a well-dispersed property even in Dulbecco's phosphate-buffered saline and do not aggregate for a period of at least 20days. The structure, morphology and assembly mechanism are systematically studied by (29)Si MAS NMR, FT-IR, (1)H NMR, SEM, FE-TEM, DLS and AFM, and the change in assemblies during the drug release is monitored using FE-TEM images. MTT assays indicate that the assemblies only have low cytotoxicity, while CLSM and TEM observations reveal that the assemblies can easily penetrate cultured human endothelial cells. When clopidogrel is used as a guest molecule, the assemblies show not only much higher loading capacities compared to MTM and other containing β-CD assemblies or nanoparticles, but also a sustained release of clopidogrel up to 30days. This is attributed to the fact that the guest molecule is both supramolecularly complexed within the dendritic scaffold and intercalated into CD and MTM hosts. Host-guest systems between assemblies and various guests hold promising applications in drug delivery system and in the biomedical fields.

Self-assembled clay films with a platelet-void multilayered nanostructure and flame-blocking properties

Polymeric composite films with a high loading of nano-size silicates can hardly meet the increasingly stringent fireproof and smoke-free requirements during burning. Thus, it is desirable to prepare pure clay films that can block air, heat, and flame. Here we report an organic-free clay film capable of both flame- and heat-shielding. The film was prepared from the self-assembly of nanometer-thick silicate platelets derived from the exfoliation of natural clays. The self-assembled film has a highly regular multilayered nanostructure over a large area and an appreciable volume of air entrapped in between. The combination of regular structure and substantial air volume contributes to the low thermal conductivity and flame blocking property of the film. It was demonstrated that the film can shield flame over hour duration and prevent temperature rising on the backside of film. This remarkable clay film has a myriad of uses including gas barrier, heat insulator, and fireproof devices.