Molybdovanadophosphoric Acid Catalyzed Oxidation of Hydrocarbons by H2O2 to Oxygenates

Heteropoly acids of the general formula H_3+x[PMo_12-xV_xO₄₀] (where x = 1,2,3) catalyzed the oxidation of aromatic hydrocarbons at 65°C with H₂O₂ to give oxygenated products. Among the catalysts, H₄[PMo₁₁VO₄₀] was found to be a more active catalyst and its activities have been reported in the oxidation of cyclohexane, methyl cyclohexane, naphthalene, 1-methyl naphthalene and biphenyl.     

Recent developments in the metal catalysed cross-coupling reactions for the synthesis of the enone system of chalcones

For the last two decades, chalcones and their derivatives have attracted special interest among researchers due to their pharmaceutical properties. Numerous research works have been still going on to improve the methodologies of chalcone synthesis. Chalcone has displayed a remarkable curative efficiency to cure numerous diseases and it continues to show promise for new drug investigations. This review highlights the metal catalysed cross-coupling reactions for the synthesis of chalcone and its derivatives from 2009 to 2020.     

Synthesis and characterization of azo–bisbenzylidene‐based polymers for second order nonlinear optics

Main chain polymers containing azo and bisbenzylidene moiety were synthesized by polycondensation method. The successful polymerization reaction was characterized by UV–vis absorption, FT‐IR and NMR spectroscopy. The resulting polymers were soluble in polar solvents like dimethyl formamide (DMF) and showed good thermal stability up to 250 °C. These polymers were blended with poly methyl methacrylate (PMMA) and corona poled for characterizing second harmonic generation (SHG) property. Temperature stability study of SHG intensity of poled polymer showed that it is stable up to 80 °C. To improve temperature stability further the crosslinking of polymer under UV light is proposed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4317–4324     

Adsorption Characteristics of Activated Carbon for the Reclamation of Eosin Y and Indigo Carmine Colored Effluents and New Isotherm Model

The adsorption response of eosin Y and indigo carmine acid dyes on activated carbon as a function of system temperature for a fixed concentration was investigated at various temperatures via adsorption isotherms and their thermodynamic quantities such as enthalpy, entropy, and Gibbs free energy changes. The adsorption data were exploited to develop a new adsorption isotherm. The new isotherm was developed with the spirit of solid–liquid phase equilibrium and regular solution theory. The proposed model has four adjustable constants and correlates adsorption isotherm in terms of the system temperature and melting temperature of the dye. The effect of pH on the removal of acid dyes was reported. The pH variation was observed to affect the adsorption efficiency. The removal of eosin Y and indigo carmine decreased from 99.4% to 82.6% and 92.38% to 79.48%, respectively, when the pH of the solution varied from 2 to 12. The thermodynamic analysis of the process reveals that the process of the removal of acid dyes is exothermic and spontaneous. Moreover, the kinetics parameters of the batch process are reported.     

Emission characteristics of laser dyes C1 and Rh6G in cross-linked polyvinyl alcohol solutions

The lifetimes and the relative quantum yields for fluorescence of two laser dyes Coumarin 1 and Rhodamine 6G have been determined in cross-linked polyvinyl alcohol matrix. The cross-linking has been achieved using gamma radiation. The relative fluorescence quantum yields of the dyes increased with increasing cross-linking of the polymer, but the fluorescence lifetimes remained unchanged within experimental error. The results have been attributed to a reduction in the loss of the excitation energy via the internal conversion of the excited singlet state due to increase in the viscosity of the medium brought about by the increased cross-linking of the polymer.     

Synthesis and characterization of monosubstituted and disubstituted poly(3,4‐propylenedioxythiophene) derivatives with high electrochromic contrast in the visible region

Monosubstituted and disubstituted 3,4‐propylenedioxythiophenes were synthesized and polymerized by both chemical and electrochemical methods. All the monomers were characterized for their molecular structures, and the polymers were characterized for their electrochemical properties. The disubstituted derivatives showed higher contrast than the corresponding monoalkyl derivatives. The highest electrochromic contrast of 89% was exhibited by a dibenzyl derivative, but the derivative was insoluble. On the other hand, the electrochemically polymerized dihexyl‐ and didodecyl‐substituted poly(3,4‐propylenedioxythiophene)s exhibited 74 and 77% electrochromic contrast, respectively, and were soluble. The molecular weights of the chemically and electrochemically synthesized polymers were analyzed by gel permeation chromatography. The chemically synthesized polymers showed higher molecular weights. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 419–428, 2005     

Three dimensional structure of celgard® microporous membranes

The unique three dimensional structure of Celgard® 2500 film has been shown by direct enhanced contrast transmission electron microscopy (TEM) of thin sections from the bulk and by high resolution scanning electron imaging (SEI) of the film surface. The TEM method developed includes treatment with an unsaturated surfactant, which then reacts with osmium tetroxide to form an electron dense stain. This is followed by standard microtomy and TEM observations made possible by the stability and contrast imparted by the heavy metal. Sectioning in all three dimensions — along the machine direction, across the machine direction and across the face of the membrane — gives a total view of the bulk microstructure. Preparation for high resolution SEI imaging includes metal coating with the Ion Beam Micro-Sputter gun, to form a coherent fine grain surface to dissipate charge, provide secondary electrons for imaging, and protect the sensitive polymer from beam damage. The SEI view of the surface completes the three dimensional characterization.The microporous structure of Celgard® 2500 is formed during extrusion, annealing and stretching of isotactic polypropylene. The elliptical pores formed during this process have been shown to be oriented with their major axes parallel to the machine direction and the film surface. The pores are grouped into rows or pore channels which traverse the thickness of the film at an angle to its surface and which oscillate in and out of the plane of a cross-section taken in the machine direction. The observed structure is morphologically uniform throughout the bulk of the film. However, a thin surface layer appears to exhibit a slightly smaller pore size and a lower two dimensional pore area than does the interior. Thus, the microporous structure provides a continuous, but tortuous or staggered, row configuration necessary for high fluid transport rates.     

An efficient biomimetic Fe-catalyzed epoxidation of olefins using hydrogen peroxide

A new, environmentally benign and practical epoxidation method was developed using inexpensive and efficient Fe catalysts. FeCl3.6H2O in combination with commercially available pyridine-2,6-dicarboxylic acid and amines showed excellent reactivity and selectivity towards aromatic olefins and moderate reactivity towards 1,3-cyclooctadiene utilizing H2O2 as the terminal oxidant.     

Polymer translocation in crowded environments

We study the effect of the crowded environments on the translocation of a polymer through a pore in a membrane. By systematically treating the entropic penalty due to crowding, we show that the translocation dynamics are significantly altered, leading to novel scaling behaviors of the translocation time. We also observe new and qualitatively different translocation regimes depending upon the extent of crowding, transmembrane chemical potential asymmetry, and polymer length.