Hydrolysis of schiff bases, 1: Kinetics and mechanism of spontaneous,acid, and base hydrolysis of N-(2/4-hydroxybenzylidene)-2-aminobenzothiazoles

The rate of hydrolysis of title schiff bases was studied in the pH range 4–13 in 10% dioxanewater system, CTAB, NaLS micellar solutions. The hydrolysis was found to be due to ‘water’ and ‘hydroxide’ reactions and hence the rate constants in different pH were computed and analyzed with an intermediate involving a water molecule being positioned with the help of 2-OH group and the thiazolyl C–N pi bond. The ‘hydroxide’ reaction was due to a direct nucleophilic attack of hydroxide ion at the aldimine linkage of the reactant. The influence of cationic and anionic micelles supports the mechanistic picture in the entire pH range.     

SEC‐MALDI‐TOF mass spectral characterization of a hyperbranched polyether prepared via melt transetherification

An AB₂ monomer, 1‐(2‐hydroxyethoxy)‐3,5‐bis‐(methoxymethyl)‐2,4,6‐trimethylbenzene, was synthesized from mesitol and melt‐polycondensed in the presence of an acid catalyst via a transetherification process at 145–150 °C to yield a soluble, moderately high molecular weight hyperbranched polyether. The degree of branching in the polymer was calculated to be 0.78 by a comparison of its NMR spectrum with that of an appropriately designed model compound. The weight‐average molecular weight of the hyperbranched polymer was determined to be 64,600 (weight‐average molecular weight/number‐average molecular weight = 5.2) by size exclusion chromatography (SEC) in CHCl₃ with polystyrene standards. The origin of the broad molecular weight distribution, which could either be intrinsic to such hyperbranched structures or be due to structural heterogeneity, was further probed by the fractionation of the samples by SEC and by the subjection of each fraction to matrix‐assisted laser desorption/ionization time‐of‐flight mass spectral analysis. The mass spectral analysis suggested the presence of two primary types of species: one corresponding to the simple branched structure and the other to macrocyclics. Interestingly, from the relative intensities of the two peaks, it was apparent that cyclization became favorable at higher conversions in the melt transetherification process. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4463–4476, 2002     

Classical ϕ6-field theory in (1+1) dimensions 2. Proof of the existence of domain walls above the transition point

The existence of a domain wall-like contribution to the free energy above the first order phase transition point is demonstrated for a system described by the ϕ⁶-field theory in (1+1) dimensions.     

Amine‐Templated One‐Dimensional Metal Sulfates Including a Mixed‐Valent Fe Compound with a Half‐Kagome Structure

Organically templated metal sulfates are relatively new. Six amine‐templated transition‐metal sulfates with different types of chain structures, including a novel iron sulfate with a chain structure corresponding to one half of the kagome structure, were synthesized by hydro/solvothermal methods. Amongst the one‐dimensional metal sulfates, [C₁₀N₂H₁₀][Zn(SO₄)Cl₂] ( 1 ) is the simplest, being formed by corner‐linked ZnO₂Cl₂ and SO₄ tetrahedra. [C₆N₂H₁₈][Mn(SO₄)₂(H₂O)₂] ( 2 ) and [C₂N₂H₁₀][Ni(SO₄)₂(H₂O)₂] ( 3 ) have ladder structures comprising four‐membered rings formed by SO₄ tetrahedra and metal–oxygen octahedra, just as in the mineral kröhnkite. [C₄N₂H₁₂][V^III(OH)(SO₄)₂]?H₂O ( 4 ) and [C₄N₂H₁₂][VF₃(SO₄)] ( 5 ) exhibit chain topologies of the minerals tancoite and butlerite, respectively. The structure of [C₄N₂H₁₂][H₃O][Fe^IIIFe^II F₆(SO₄)] ( 6 ) is noteworthy in that it corresponds to half of the hexagonal kagome structure. It exhibits ferrimagnetic properties at low temperatures and the absence of frustration, unlike the mixed‐valent iron sulfate with the full kagome structure.     

Facile synthesis,characterization and application of magnetic Fe3O4-coir pith composites for the removal of methyl violet from aqueous solution: Kinetics,isotherm, thermodynamics and parametric optimization

Dyes are commonly used in coloring clothes; in fertilizers, as anti-freezers, as detergents and so on. The use of such dyes has carcinogenic and genotoxic effects. These dyes require proper removal from the environment. Subsequently, a green and low-cost approach promises to adhere to sustainability of the environment while maximum removal of these toxic dyes. The present study describes removal of methyl violet (MV) dye by adsorption process magnetically separable Fe₃O₄-coir pith composites. The study was evaluated in batch system taking the optimum conditions as: pH: 7, contact time: 12 h, stirring speed: 200 rpm, concentration of dye: 100 mg/L, adsorbent weight: 3 g/L, temp.: 308 K. The central composite design approach of response surface methodology in design-expert software showed maximum removal efficiency (>98%) for optimal parameters. The experimental equilibrium data fitted reasonably well to Langmuir isotherm model. ANOVA analysis along with Fisher's statistical test was also performed to validate the model. The predicted model was at par with the experimental values with adjusted R² of 0.9914. A thorough investigation of kinetic ($R_{\text{Pseudo second order}}^2$ = 0.99; $R_{\text{Pseudo second order}}^2=0.97;R_{\text{intra}?\text{particle diffusion}}^2=0.98)$, thermodynamic, adsorption isotherm $(R_{\text{Langmuir isotherm}}^2=0.997$ $R_{\text{Freundlich isotherm}}^2=0.99$ and eco-toxicological characteristics were performed for proper evaluations of the properties as well as sustainability of the adsorbent material. The whole research indicated encouraging potential of the developed material for adsorption, reusability and sustainability in applications for industrial scale wastewater treatment.     

Investigation of complex impedance and modulus properties of Nd doped 0.5BiFeO3-0.5PbTiO3 multiferroic Composites

0.5BiNd _x Fe_1?x O ₃ ? 0.5PbTiO₃ (BN _x F_1?x ? PT)(x = 0.05, 0.10, 0.15, 0.20) composites were successfully synthesized by a solid state reaction technique. At room temperature, X-ray diffraction shows tetragonal structure for all concentrations of Nd doped 0.5BiFeO₃ ? 0.5PbTiO₃ composites. The nature of Nyquist plot confirms the presence of bulk effects only for BN _x F_1?x ? PT (x = 0.05, 0.10, 0.15, 0.20) composites. The bulk resistance is found to decreases with the increasing temperature as well as Nd concentration and exhibits a typical negative temperature coefficient of resistance (NTCR) behavior. Both the complex impedance and modulus studies have suggested the presence of non-Debye type of relaxation in the composites. Conductivity spectra reveal the presence of hopping mechanism in the electrical transport process of the composites. The activation energy calculated from impedance plot of the composite decreases with increasing Nd _x concentration and found to be 0.89, 0.76, 0.71 and 0.70 eV for x=0.05, 0.10, 0.15 and 0.20 respectively.     

Role of the Surfactant Structure in the Behavior of Hydrophobic Ionic Liquids within Aqueous Micellar Solutions

The behavior of an ionic liquid (IL) within aqueous micellar solutions is governed by its unique property to act as both an electrolyte and a cosolvent. The influence of the surfactant structure on the properties of aqueous micellar solutions of zwitterionic SB‐12, nonionic Brij‐35 and TX‐100, and anionic sodium dodecyl sulfate (SDS) in the presence of the “hydrophobic” IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF₆]) is assessed along with the possibility of forming oil‐in‐water microemulsions in which the IL acts as the “oil” phase. The solubility of [bmim][PF₆] within aqueous micellar solutions increases with increasing surfactant concentration. In contrast to anionic SDS, the zwitterionic and nonionic surfactant solutions solubilize more [bmim][PF₆] at higher concentrations and the average aggregate size remains almost unchanged. The formation of IL‐in‐water microemulsions when the concentration of [bmim][PF₆] is above its aqueous solubility is suggested for nonionic Brij‐35 and TX‐100 aqueous surfactant solutions.     

Strain-tunable band parameters of ZnO monolayer in graphene-like honeycomb structure

We present ab initio calculations which show that the direct-band-gap, effective masses and Fermi velocities of charge carriers in ZnO monolayer (ML-ZnO) in graphene-like honeycomb structure are all tunable by application of in-plane homogeneous biaxial strain. Within our simulated strain limit of ±10%$\pm 10\text{\%}$, the band gap remains direct and shows a strong non-linear variation with strain. Moreover, the average Fermi velocity of electrons in unstrained ML-ZnO is of the same order of magnitude as that in graphene. The results promise potential applications of ML-ZnO in mechatronics/straintronics and other nano-devices such as the nano-electromechanical systems (NEMS) and nano-optomechanical systems (NOMS).     

A Ni2+ (S = 1) Kagome compound templated by 1,4-diazacubane [corrected

1,8-Diazacubane-templated nickel(II) sulfate with the Kagome structure prepared under solvothermal conditions exhibits interesting magnetic properties.