Adhigan Murali

Sol-gel network silica/modified montmorillonite clay hybrid nanocomposites for hydrophobic surface coatings.

Sol-gel silica/nanoclay composites were prepared through sol-gel polymerization technique using tetraethylorthosilicate precursor and montmorillonite (MMT) clay in aqueous media. In this study, both montmorillonite-K(+) and organically modified MMT (OMMT) clays were used. The prepared composites were coated on glass substrate by making 1 wt% solution in ethyltrichlorosilane. The incorporation of nanoclay does not alter the intensity of characteristic Si-O-Si peak of silica network. Thermogravimetric studies show that increasing clay content increased the degradation temperature of the composites. Differential scanning calorimetry (DSC) results of organically modified MMT nanoclay incorporated composite show a shift in the melting behavior up to 38°C. From DSC thermograms, we observed that the ΔH value decreased with increasing clay loading. X-ray diffraction patterns prove the presence of nanoclay in the composite and increase in the concentration of organically modified nanoclay from 3 to 5 wt% increases the intensity of the peak at 2θ=8° corresponds to OMMT. Morphology of the control silica gel composite was greatly influenced by the incorporation of OMMT. The presence of nanoclay changed the surface of control silica gel composite into cleaved surface with brittle in nature. Contact angle measurements were done for the coatings to study their surface behavior. These hybrid coatings on glass substrate may have applications for hydrophobic coatings on leather substrate.

The reinforced hydrogel for drug loading: immobilization of single-walled carbon nanotubes in cross-linked polymers via multiple interactions

We report a facile method to prepare novel carbon nanotube (CNT)-based hydrogels in an aqueous environment. To maximize the bonding between nanotubes and polymers, we exploited several non-covalent interactions like ionic, π–π stacking, hydrophobic, H-bonding, etc. Importantly, the nano-hydrogels swell in both water and organic solvents. The materials showed improvements in various physicochemical properties. The new material is fairly biocompatible, as shown by MTT assay studies. It is also a useful material to load a water-soluble drug or micronutrient such as riboflavin (vitamin B2) or amitriptyline hydrochloride. The releasing study of the drug clearly showed pH responsive behaviour.

Chromium-assisted immobilization of N-isopropylacrylamide-based methacrylic acid copolymers on collagen and leather surfaces: thermo-responsive behaviour

In the present paper, we report the non-covalent immobilization of pH and temperature responsive poly(N-isopropylacrylamide)-co-methacrylic acid on a protein collagen (type I) and a leather surface. The polymer has N-isopropylacrylamide (NIPAM) functionality that is responsible for the thermo-responsive characteristics and carboxylic acid/carboxylate functionality that facilitates the pH-responsive behaviour. We were able to tune the clouding behaviour of the polymer in water from 15 to 40 °C by changing the pH from 4.5 to 5.7. The binding of the polymer to a native collagen protein (type I) or leather is facilitated by the carboxylate groups that form coordination complexes with chromium(III). The polymer was successfully used in the retanning and coating of leather. The polymer-coated leather as well as the polymer-grafted collagen clearly show thermo-responsive characteristics.

Augmentation of properties on sparingly loaded nanocomposites via functionalized single-walled carbon nanotubes using a covalent approach

Polymer nanocomposites are developed, for the first time, as transparent films by the covalent addition of polyurethane (PU) prepolymers to trace amounts of functionalized carbon nanotubes, [OH]n–SWCNTs, via an efficient route using mild reagents. These PU nanocomposites, which were uniformly distributed with SWCNTs via covalent bonding between SWCNTs and the polyurethane network show enhanced mechanical, thermal and conductivity (10−4 S cm−1) properties.

Carbon Nanotube Reinforced Polymer-Stabilized Liquid Crystal Device: Lowered and Thermally Invariant Threshold with Accelerated Dynamics

Polymer-stabilized liquid crystal (PSLC) devices comprise a polymer matrix in an otherwise continuous phase of liquid crystal. The fibrils of the polymer provide, even in the bulk, virtual surfaces with finite anchoring energy resulting in attractive electro-optic properties. Here, we describe a novel variation of the PSLC device fabricated by reinforcing the polymer matrix with polymer-capped single-walled carbon nanotubes (CNTs). The most important outcome of this strengthening of the polymer strands is that the threshold voltage associated with the electro-optic switching becomes essentially temperature independent in marked contrast to the significant thermal variation seen in the absence of the nanotubes. The reinforcement reduces the magnitude of the threshold voltage, and notably accelerates the switching dynamics and the effective splay elasticity. Each of these attributes is quite attractive from the device operation point of view, especially the circuit design of the required drivers. The amelioration is caused by the polymer decorating CNTs being structurally identical to that of the matrix. The resulting good compatibility between CNTs and the matrix prevents the CNTs from drifting away from the matrix polymer, a lacuna in previous attempts to have CNTs in PSLC systems. The difference in the morphology, perhaps the primary cause for the effects seen, is noted in the electron microscopy images of the films.

Enhancement of the physicochemical properties of polyurethane–perovskite nanocomposites via addition of nickel titanate nanoparticles

Polyurethane (PU)–perovskite nanocomposite films were developed by in situ addition of nickel titanate nanoparticles (NiTiO3 NPs) into a PU matrix formulation. Among the three samples of NiTiO3 NPs calcinated at 400, 600 and 800 °C, the pertinent rhombohedral phase of NiTiO3 has been achieved at 800 °C. NiTiO3 is loaded in trace amounts (0.5 wt%) with the PU matrix to cast as films (thickness ∼ 1.5 mm), which demonstrate its influence on PU, studied by ATR-IR, Raman, UV-vis DRS, XRD, TGA, DSC, XPS, AFM, SEM, optical microscopy, vibrating sample magnetometer (VSM) and impedance spectroscopy. The characteristics of the PU–NiTiO3 nanocomposite films are compared with a control PU film, and these reveal the enhancement in thermal stability (>10 °C), electrical conductivity (8.72 × 10−5 S cm−1) and mechanical strength (19.7 ± 0.8 MPa) as well as the effect on magnetic and optical properties due to non-covalent interactions upon uniform distribution of NiTiO3 on the PU film.

Synthesis of Fluorophore Decorated Single-Walled Carbon Nanotubes for In-Vitro Cytocompatibility

We report rhodamine based fluorophore derivative for the stable dispersion of single-walled carbon nanotubes (SWCNTs), which can afford better fluorescent label to carbon nanotubes (CNTs). The nanotubes-fluorophore conjugates are helpful in achieving stable dispersion in polar and non-polar solvents with intense fluorescence. The product was characterized through NMR, Mass spectrometry, Raman, XPS, SEM, AFM and Fluorescence measurements. The formation of SWCNT-g- Rhodamine was confirmed by the presence of D and G bands in Raman spectrum. The alkyl and aryl groups in the range of 14.8, 17.6, 38.1 and 96.3 ppm confirms the grafting of the nanocomposite through NMR. The morphological studies were carried out intensively for analyzing SWCNTs stable dispersion and the results from EDAX measurements shows the elements weight% of C: 35.09 and N: 30.1 concludes that SWCNTs are completely grafted onto rhodamine derivatives. The application of SWCNTs fluorophore conjugates were analyzed by cell viability studies using MTT assay and exhibits less toxic compare to other functionalized CNTs. The viability of percentage increases with decrease in the concentration of SWCNT-COCl with 91.7% of live cells even after 24 h at a concentration of 250 μg for SWCNT-g-Rhodamine. The fluorescent images obtained during viability analysis shows enhanced fluorescence for living cells in case of SWCNT-g-Rhodamine compared to SWCNT-COCl, which clearly shows the utility of decorating nanotubes with fluorophore. This research work further extends its application for molecular sensing and other biological process.

Synthesis and characterization of nitrogen-rich azo-linked conjugated polymer materials

ABSTRACT Efficient azo-linked polymers of 2,4,6-tris(4-nitrophenyl)pyridine-melamine (TNPP-M), and 2,4,6-tris(4-nitrophenyl)pyridine-sulfanilamide (TNPP-S) were prepared by condensation polymerization technique from TNPP-based monomer reacting with amines as melamine and sulfanilamide. The synthesized polymer structure was confirmed by various experimental techniques, such as Fourier transform infrared spectroscopy, solid-state 13C NMR, and X-ray diffraction (XRD). Particle size was calculated using Williamson–Hall (W–H) plot from powder XRD pattern. The thermal analysis and scanning electron microscopy of TNPP-S polymer displayed an excellent thermal stability and capsule-like morphology was observed. UV/visible absorptions of TNPP-S and TNPP-M polymers exhibit two bands, a strong band at 365 nm, and a shoulder at 385 nm for TNPP-M; these polymeric semiconducting materials could be useful for solar fuel cell applications.