Thermogravimetric study of n-alkylammonium-intercalated montmorillonites of different cation exchange capacity

Three n-alkylammonium salts of varying alkyl chain length were ion exchanged with montmorillonites (MMT) of different cation exchange capacity (CEC). The intercalated MMTs were characterized by thermogravimetry (TG), XRD, FTIR to acquire an insight into the intergallery structural arrangement of the organic alkylammonium cations (AAC). The increment in the intergallery spacing from XRD pattern was correlated with chain length and interlayer arrangement of AAC. Multiple organic mass-loss stages in thermogravimetric analysis indicate two types of anchorage of AAC in intercalated clay. CEC of MMT was found to influence the intergallery confinement and excess adsorption of AAC

Simultaneous intercalation of two quaternary phosphonium salts into montmorillonite

Intercalation of montmorillonites with a mixture of intercalates has not been studied extensively. The objective of the present investigation was to study the effects of phosphonium-based intercalate mixtures on the properties (organic loading and basal spacing) of montmorillonite. These phosphonium-intercalated montmorillonites are promising candidates as high-temperature stable nanofillers for application in clay polymer nanocomposites. Two salts with different cationic heads and chain lengths were mixed in varying molar ratios and the mixtures were intercalated into the interlayer space of montinorillonite. Two sets were chosen based on the chain length and the cationic head-group structure of the two intercalated salts (referred to hereafter as set 1 and set 2). The resultant intercalated montmorillonite was characterized by thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The organic loading of the intercalated montmorillonite increased with the proportion of longer carbon-chain intercalate in the mixture. The intensity of the characteristic XRD peak of each intercalate varied with the mole fraction percent of that intercalate in the solution mixture. No marked synergistic effect of the intercalate mixture on the basal spacing and organic loading properties of the intercalated montmorillonite was observed the proportional influence of individual components was found to be more prominent

Thermal degradation of alkyl triphenyl phosphonium intercalated montmorillonites

The decomposition mechanism of intercalated montmorillonites at a particular temperature region and the activation energy involved in it are the two important aspects which determines the thermal stability of intercalated montmorillonites. In this study, montmorillonite was intercalated with alkyl (methyl, ethyl, propyl, and dodecyl) triphenyl phosphonium intercalates. Differential thermogravimetric analysis of each intercalated montmorillonites showed different peaks with associated organic loss at different temperature zone. Intercalated montmorillonites were subjected to isothermal kinetic analysis corresponding to selected temperature zone obtained from DTG peaks. Activation energies of organic decomposition process at selected temperature zones were determined. Mass spectral analysis and FTIR were done to understand the decomposition mechanisms and to relate them with the estimated activation energies

Characterization of 1,3-dialkyl imidazolium intercalated montmorillonites

Na-Montmorillonite (Na-MMT) was intercalated with two series of dialkyl imidazolium salts. The series were selected by varying the alkyl substitutions at 1 and 3 positions of imidazole ring viz. 1-alkyl 3-methyl imidazolium salts in one series and 1-methyl 3-alkyl imidazolium salts in other series. Length of the alkyl chain was varied. Gallery heights of these imidazolium intercalated montmorillonites (I-MMT) were deduced by X-ray diffraction analysis (XRD). Thermal stability and organic loading of I-MMT were studied using thermogravimetric analysis. Vibration bands due to organic inclusion within montmorillonites (MMT) were characterized by FTIR measurements. TEM analysis disclosed the microstructural changes of MMT after intercalation with organic intercalates. The properties of I-MMT were found to be influenced by alkyl chain length and their variation in 1 and 3 positions of imidazole ring

Organophilic nano clay: A comprehensive review

Organophilic nano clay is an important organic-inorganic hybrid derived from intelligent combination of two dissimilar components, viz, clays and organic molecules, at the nanometric and molecular level. The clay component of this hybrid provides a 2-D lamellar structure with interesting surface chemistry, which can be engineered by organic molecules. 2:1 layered clay minerals with high cation exchange capacity, e.g. montmorillonite, possess cation exchange sites on the siloxane surface which can be exchanged with suitable organic molecules. Key aspect of this organic treatment is to swell the interlayer space of the clay mineral up to a certain extent reducing interlayer interaction, to produce nanoplatelet of aluminosilicate materials. Those engineered nanoplatelets are used in various fields of applications, viz, polymer nano clay composite, rheological modifier, thickening and gelling agent in paints and lubricants, in waste water treatment, and also as drug delivery vehicle. Intensive research activity in this complex system is attested by evergrowing number of symposia, books and specialized journals devoted to this subject. This present article is an updated review of organophilic nano clay preparation, characterization and application of the material. Important information available in the protected domain of patent is also included

ORGANIC-INORGANIC HYBRIDS PREPARED FROM ALKYL PHOSPHONIUM SALTS INTERCALATED MONTMORILLONITES

Present investigation is focused on systematic and detailed characterization of alkyl phosphonium intercalated montmorillonite (MMT). The objective of the work is to provide a better understanding of the specific changes in properties of the hybrid material with changes in structure of incoming organic cations. In the present work, Na-MMT was intercalated with phosphonium salts of two different cationic head compositions namely alkyl triphenyl and alkyl tributyl groups. Length of alkyl chain was also varied. Resultant organic-inorganic hybrids were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Thermogravimetry (TG) and Fourier transformed infrared spectroscopy (FTIR). Effective volume occupied by the cationic heads influenced interlayer arrangements. Intercalated MMT with two different cationic heads behaved differently in relation to thermal decomposition patterns. Possible explanation was given based on hybridization of bonds. Van der Waals attachment of alkyl chains influenced the interlayer stacking and organic loading. Attempts were made to correlate the changes in properties of intercalated MMT with the structural aspects of incoming organic cations

Boranephosphonate DNA-Mediated Metallization of Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs), when dispersed in DMSO with boranephosphonate DNA (bpDNA), were efficiently metalized with silver, gold, and palladium nanoparticles (NPs). This was possible by first adsorbing boranephosphonate DNA onto the surface of SWNTs and then bathing with silver, gold, and palladium metal salts, which form the corresponding nanoparticles by reduction of their respective ions without addition of any external reducing agent. Reduction of a redox dye, 2,6-dichlorophenolindophenol (DCPIP), by Pd nanoparticle conjugates (PdNP/bpDNA/SWNT) disclosed the efficient electron transfer properties of these metallized SWNTs. These PdNP/bpDNA/SWNT conjugates were also successfully used to catalyze Heck and Suzuki coupling reactions. Boranephosphonate DNA-mediated metallization of SWNTs therefore provides a new method for fabricating well-defined SWNT-based nanostructures. This discovery should reveal unexpected applications in various research areas ranging from nanoelectronic devices to nanoscale SWNT supported multimetallic catalysts having different compositions

Formation of Silver Nanostructures by Rolling Circle Amplification Using Boranephosphonate-Modified Nucleotides

We investigate the efficiency of incorporation of boranephosphonate-modified nucleotides by phi29 DNA polymerase and present a simple method for forming large defined silver nanostructures by rolling circle amplification (RCA) using boranephosphonate internucleotide linkages. RCA is a linear DNA amplification technique that can use specifically circularized DNA probes for detection of target nucleic acids and proteins. The resulting product is a collapsed single-stranded DNA molecule with tandem repeats of the DNA probe. By substituting each of the natural nucleotides with the corresponding 5′-(α-P-borano)­deoxynucleosidetriphosphate, only a small reduction in amplification rate is observed. Also, by substituting all four natural nucleotides, it is possible to enzymatically synthesize a micrometer-sized, single-stranded DNA molecule with only boranephosphonate internucleotide linkages. Well-defined silver particles are then readily formed along the rolling circle product