Studies on thermal and morphological properties of 1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane-epoxy-bismaleimide matrices

A new cyanate ester monomer, 1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane has been synthesized and characterized. Epoxy modified with 4, 8 and 12% (by weight) of cyanate ester were made using epoxy resin and 1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane and cured by using diaminodiphenylmethane. The cyanate ester modified epoxy matrix systems were further modified with 4, 8 and 12% (by weight) of bismaleimide (N,N′-bismaleimido-4,4′-diphenylmethane). The formation of oxazolidinone and isocyanurate during cure reaction of epoxy and cyanate ester blend was confirmed by IR spectral studies. Bismaleimide-cyanate ester-epoxy matrices were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and heat deflection temperature (HDT) analysis. Thermal studies indicate that the introduction of cyanate ester into epoxy resin improves the thermal degradation studies at the expense of glass transition temperature. Whereas the incorporation of bismaleimide into epoxy resin enhances the thermal properties according to its percentage content. However, the introduction of both cyanate ester and bismaleimide influences the thermal properties according to their percentage content. DSC thermogram of cyanate ester modified epoxy and bismaleimide modified epoxy show unimodel reaction exotherms. The thermal degradation temperature and heat distortion temperature of the cured bismaleimide modified epoxy and cyanate ester-epoxy systems increased with increasing bismaleimide content. The morphology of the bismaleimide modified epoxy and cyanate ester-epoxy systems were also studied by scanning electron microscopy. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation and characterization of bismaleimide/1,3-dicyanatobenzene modified epoxy intercrosslinked matrices

An intercrosslinked network of cyanate ester (CE)-bismaleimide (BMI) modified epoxy matrix system was made by using epoxy resin, 1,3-dicyanatobenzene and bismaleimide (N,N^′-bismaleimido-4,4^′-diphenyl methane) with diaminodiphenylmethane as curing agent. BMI-CE-epoxy matrices were characterised using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and heat deflection temperature (HDT) analysis. The matrices, in the form of castings, were characterised for their mechanical properties such as tensile strength, flexural strength and unnotched Izod impact test as per ASTM methods. Mechanical studies indicated that the introduction of cyanate ester into epoxy resin improves the toughness and flexural strength with reduction in tensile strength and glass transition temperature, whereas the incorporation of bismaleimide into epoxy resin influences the mechanical and thermal properties according to its percentage content. DSC thermograms of cyanate ester as well as BMI modified epoxy resin show an unimodal reaction exotherm. Electrical properties were studied as per ASTM method and the morphology of the BMI modified epoxy and CE-epoxy systems were studied by scanning electron microscope.     

Synthesis and characterization of fluorine functionalized graphene oxide dispersed quinoline-based polyimide composites having low-k and UV shielding properties

Polyimide nanocomposites having low-k and UV shielding properties have been developed using fluorine functionalized graphene oxide and bis(quinoline amine) based polyimide. The polyimide was synthesized using bis(quinoline amine) and pyromellitic dianhydride at appropriate experimental conditions, and its molecular structure was confirmed through various spectral analysis such as FTIR and NMR. The polyimide (PI) composites were prepared using bis(quinoline amine), pyromellitic dianhydride, and separately filled with 1, 5, 10 wt% of fluorinated graphene oxide (FGO) through in situ polymerization. The polymer composites were characterized using thermo gravimetric analysis (TGA), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). In addition, the water contact angle, dielectric behavior, and UV–Vis shielding behavior of FGO/PI composites were evaluated. The value of the water contact angle of the polyimide was increased with increment of FGO in the polyimide matrix. The highest water contact angle of polyimide composites observed 108° was obtained for 15 wt% FGO reinforced polyimide composite. The value of the dielectric constant for neat, 1, 5, and 15 wt% FGO reinforced polyimide composites was obtained as 4.5, 3.7, 2.6, and 2.0, respectively. It is also observed from by UV–Vis spectroscopy analysis that the FGO reinforced polyimide composites have good UV shielding behavior.     

Optical and dielectric studies on succinic acid single crystals

Single crystals of ferroelectric succinic acid (SA) with very high degree of transparency were grown from aqueous solution by slow evaporation technique. Single crystal X‐ray diffraction analysis reveals that the crystal belongs to monoclinic system with the space group P2₁/c. Some physical parameters have been determined for grown crystal. The optical absorption study reveals the transparency of the crystal in the entire visible region and the cut off wave length was found to be 240 nm. The optical band gap is found to be 3.75 eV. The dependence of extinction coefficient (k) and refractive index (n) on the wavelength have also been reported. The presence of functional groups was determined qualitatively by using Fourier transform infrared spectrum (FTIR) from which force constant has been calculated. The dielectric constant was also studied as a function of frequency at room temperature and electrical conductivity has been calculated from the Cole‐Cole plot. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Morphology Controlled Synthesis of Zinc Oxide Nanostructures Through Millettia pinnata (MP) Leaf Extract as Capping Agent and its Photocatalytic Degradation Efficiency of a Textile Dye

Journal of Cluster Science - The present work reports low cost, rapid synthesis of ZnO nanostructures capped with Millettia pinnata leaf extract which produced rods, pyramids, cones and flower like...     

Investigations of crystalline and optical perfection of SHG oriented KDP crystals

Potassium dihydrogen phosphate (KDP) crystals grown along the type-II phase-matching direction were investigated for crystalline and optical perfection. High-resolution X-ray diffraction (HRXRD) technique was used for investigating crystalline perfection. UV–VIS transmission, Mach–Zehnder interferometry, birefringence interferometry and conoscopy were performed for optical characterization. HRXRD results show that the grown crystals have good structural perfection. A uniform transmittance of 92% was observed in the visible region of the spectrum. Straight and parallel fringes were observed in Mach–Zehnder interferometric studies. A symmetrical fringe pattern was obtained in conoscopy images. These interferometric results suggest that the optical homogeneity of the grown crystal was good and not influenced by the growth technique.     

Preparation and characterization of graphene nanosheets dispersed pyrrole-chorobenzaldehyde-heptaldehyde conjugated terpolymer nanocomposites for DNA detection

A new conductive terpolymer/graphene nanosheet hybrid composite has been synthesized by polymerizing pyrrole, chlorobenzaldehyde, and heptaldehyde (PPyCB&;H), in the presence of graphene nanosheets (GNS), using p-toluene sulfonic acid as a catalyst. Fourier transform infrared spectra, proton nuclear magnetic resonance, transmission electron microscopy, and X-ray diffraction patterns confirm the formation of PPyCB&;H/GNS hybrid nanocomposites. Further, the resultant nanocomposite material is coated on ITO to construct an electrochemical sensor for the reliable detection of single-strand DNA (tDNA) which is cleaved from the genomic DNA of Escherichia coli. Under optimized conditions, linear detection of genomic DNA (tDNA) with concentration ranging from 1.3 × 10⁻¹² to 1.3 × 10⁻²³ M is observed and it is repeatable with a 1.3 × 10⁻²³ M lowest level detection limit. The present modified electrode of PPyCB&;H/GNS may show utility for constructing highly sensitive electrochemical sensors for the detection of E. coli.

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Organic-inorganic hybrid fluorescent sensor thin films of rhodamine B embedded Ag-SBA 15 for selective recognition of Hg (Ⅱ) ions in water

Nowadays, the rapid and effective detection of low doses of heavy metal pollutants in contaminated water is a timely challenge in environmental pollution research. In this study, a rapid and highly sensitive assay for the detection of Hg~(2+)based on quenching of metal-enhanced fluorescence of rhodamine B(RB)has been fabricated. RB and silver nanoparticle were incorporated into the mesoporous siliceous framework spin cast on a quartz glass through post-synthetic incorporation method. The morphology and crystallinity of mesoporous structure and Ag nanoparticle were characterized by transmission electron microscopy and X-ray diffraction analyses. Photoluminescence assays on the hybrid thin film of RB-Ag-SBA15 showed a high enhancement when compared to the intensity of silver free SBA15-RB in the wavelength of 575 nm. The fluorescence of RB-Ag-SBA15 thin film decreased gradually with the increase in the concentration of Hg~(2+)and the detection limits were 10.54 nmol/L. Furthermore, the fluorescence intensity increased linearly with the concentration of Hg~(2+)in the range from 1.0 ? 10à8mol/L to10 ? 10à8mol/L, with a response time of a few seconds. In addition, this system offers a high selectivity over interfering cations such as Cd~(2+) and Pb~(2+). Overall, we have developed an optical assay having a wellordered mesoporous SBA15 containing Ag-RBfor selective detection of Hg~(2+)in aqueous solution. The scheme combines the advantages of specific binding interactions between Hg~(2+)and RB molecule and optical emission properties of RB. The method is suitable for a single-shot and irreversible analytical assay in a quartz glass/microtiter plate.     

Optical and dielectric studies on pure and Ni2+, Co2+ doped single crystals of bis thiourea cadmium chloride

Good quality single crystals of Ni²⁺, Co²⁺ ions doped Bisthiourea Cadmium Chloride (BTCC) are some of the excellent and efficient non‐linear optical materials grown from aqueous solution by slow evaporation method. The lattice parameters of the grown crystals are determined by single crystal X‐ray analysis. UV spectral analyses on these samples reveal the improved transparency of the doped crystals ascertaining the inclusion of metal ion in the lattice. FTIR spectral analysis carried out on the materials confirm the presence of functional groups. Dielectric measurements reveal that the dielectric constant of pure and doped crystals decreases with increase of frequency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on the optical and mechanical properties of organic nonlinear optical 1-(4-fluorostyryl)-4-nitrostilbene (FNS) single crystal

A new organic nonlinear optical material 1-(4-fluorostyryl)-4-nitrostilbene (FNS) has been synthesized and single crystals of FNS were grown using solvent evaporation solution growth technique (SESGT) by 2-butanon solvent. Single crystal x-ray diffraction analysis reveals the unit cell parameters of the grown crystal are a = 9.494(4) Å, b = 9.864(2) Å, c = 19.501(7) Å and it belongs to monoclinic system with noncentrosymmetric space group. Optical transmittance of the grown crystal has been studied by UV-Vis-NIR spectrum. The optical properties of FNS have been studied by means of optical transmittance measurements in the wavelength range of 190–1100 nm The optical constants were calculated from the optical transmittance (T) data such as refractive index (n), extinction coefficient (k) and reflectance (R). The optical band gap (E_g) of FNS is 3.27 eV with direct transition. The complex dielectric (?) constant of the grown FNS crystal was determined. The second harmonic generation (SHG) efficiency of the grown FNS crystal has been studied by using Kurtz-Perry powder technique and it shows 12 times relatively greater than KDP.