Miscibility studies of PVC/Aramid blends

Blends containing PVC and aramid (Ar) matrices were probed for their miscibility. In this respect, Ar chains were synthesized by aromatic diamine and diacid chloride in amide solvent. The Ar thus synthesized was characterized through Fourier transform infrared (FTIR) spectroscopy and molecular weight determination. Blend system Ar/PVC was investigated over a range of Ar/PVC ratios. Their mechanical profiles in terms of maximum stress, maximum strain, toughness, and initial moduli have been explored. Thermal properties and morphology of the blends were estimated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). A good correlation was observed between thermal, mechanical, and morphological properties of the blends. The presence of hydrogen bonding among polymers was evaluated through FTIR spectroscopy, which is believed to be responsible for the blend miscibility. Optimal thermal and mechanical profiles were depicted by the blend containing 40-wt% PVC in the Ar matrix.     

Chiral S‐stannyl dithiophosphates and dithiophosphonates on the basis of monoterpenols

Chiral S‐tributylstannyl dithiophosphates and dithiophosphonates were obtained by the reactions of optically active dithiophosphoric and dithiophosphonic acids containing (S)‐(–)‐menthyl and (R)‐(+)‐menthyl substituents with gaseous ammonia and tributyl chlorostannane. The reactions of chiral ammonium dithiophosphate containing (1R)‐endo‐(+)‐fenchyl substituent with tributyl chlorostannane or tetrachlorostannane result in corresponding S‐tributylstannyl dithiophosphate or tetrakis(dithiophosphato)stannane. Molecular structure of ammonium O,O‐di‐(–)‐menthyldithiophosphate was studied by X‐ray single crystal diffraction. Bactericidal activity of S‐tributylstannyl dithiophosphates was tested.     

Kinetics of Lab Prepared Manganese Oxide Catalyzed Oxidation of Benzyl Alcohol in the Liquid Phase

The oxidation of benzyl alcohol in the liquid phase was studied over manganese oxide catalyst using molecular oxygen as an oxidant. Manganese oxide was prepared by a mechanochemical process in solid state and was characterized by chemical and physical techniques. The catalytic performance of manganese oxide was explored by carrying out the oxidation of benzyl alcohol at 323–373 K temperature and 34–101 kPa partial pressure of oxygen. Benzaldehyde and benzoic acid were identified as the reaction products. Typical batch reactor kinetic data were obtained and fitted to the Langmuir–Hinshelwood, Eley–Rideal, and Mars–van Krevelene models of heterogeneously catalyzed reactions. The Langmuir–Hinshelwood model was found to give a better fit. Adsorption of benzyl alcohol at the surface of the catalyst followed the Langmuir adsorption isotherm. The heat of adsorption for benzyl alcohol was determined as –18.14 kJ mol^?1. The adsorption of oxygen followed the Temkin adsorption isotherm. The maximum heat of adsorption for oxygen was –31.12 kJ mol^?1. The value of activation energy was 71.18 kJ mol^?1, which was apparently free from the influence of the heat of adsorption of both benzyl alcohol and oxygen.     

Inclusion of aramid chains into the layered silicates through solution intercalation route

Aramid–organoclay nanocomposites were fabricated through solution intercalation technique. Montmorillonite was modified with p-amino benzoic acid in order to have compatibility with the matrix. The effect of clay dispersion and the interaction between clay and polyamide chains on the properties of nanocomposites were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing of thin films, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and water uptake measurements. Excessive clay dispersion was achieved even on the addition of high proportions of clay. The structural investigations confirmed the formation of delaminated nanostructures at low clay contents and disordered intercalated morphology at higher clay loadings. The tensile behavior and thermal stability significantly amplified while permeability reduced with increasing dispersibility of organoclay in the polyamide matrix.     

Interfacial Behavior of Cysteine between Mild Steel and Sulfuric Acid as Corrosion Inhibitor

Interfacial behavior of cysteine (Cys) between mild steel and sulfuric acid solution as a corrosion inhibitor has been studied with electrochemical AC (alternating current) and DC (direct current) techniques at (25.0±0.1) °C. The AC impedance results were evaluated using equivalent circuits in which a constant phase element (CPE) has been replaced with double layer capacitance (C_dl) to represent the frequency distribution of experimental data. Changes in impedance parameters (charge transfer resistance and double layer capacitance) indicated that cysteine molecules acted by accumulating at the metal/solution interface. The fractional coverage of the metal surface () was determined using AC impedance results and it was found that the adsorption of cysteine on the mild steel surface followed a Langmuir isotherm model with a standard free energy of adsorption (ΔG⁰_ads) of −35.1 kJ·mol⁻¹.To clarify the type of interaction between mild steel surface and cysteine molecules with a molecular orbital approach, electronic properties, such as, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy, and the frontier molecular orbital coefficients have been calculated. Energy gaps for the interaction of mild steel surface and cysteine molecules (E_{LUMO Fe}−E_{HOMO Cys} and E_{LUMO Cys}−E_{HOMO Fe}) were used to determine whether cysteine molecules acted as electron donors or electron acceptors when they interacted with the mild steel surface. The local reactivity was evaluated through the condensed Fukui indices. Theoretical calculations were carried out using the density functional theory (DFT) at B3LYP level with the 6-311++G(d,p) basis set for all atoms by Gaussian 03W program.     

Stacking effects on local structure in RNA: changes in the structure of tandem GA pairs when flanking GC pairs are replaced by isoG-isoC pairs

The Watson-Crick-like isoG-isoC (iGiC) pair, with the amino and carbonyl groups transposed relative to the Watson-Crick GC pair, provides an expanded alphabet for understanding interactions that shape nucleic acid structure. Here, thermodynamic stabilities of tandem GA pairs flanked by iGiC pairs are reported along with the NMR structures of the RNA self-complementary duplexes (GCiGGAiCGCA)2 and (GGiCGAiGCCA)2. A sheared GA pairing forms in (GCiGGAiCGCA)2, and an imino GA pairing forms in (GGiCGAiGCCA)2. The structures contrast with the formation of tandem imino and sheared GA pairs flanked by GC pairs in the RNA self-complementary duplexes (GCGGACGC)2 and (GGCGAGCC)2, respectively. In both iGiC duplexes, Watson-Crick-like hydrogen bonds are formed between iG and iC, and iGiC substitutions result in less favorable loop stability. The results provide benchmarks for testing computations of molecular interactions that shape RNA three-dimensional structure.     

X-ray absorption near edge structure and crystallographic studies of the mixed valence oxide SrRu0.8Ni0.2O3

Neutron diffraction methods are used to refine the structure of SrRu(0.8)Ni(0.2)O(3) at room temperature and 4 K. X-ray absorption measurements at the Ru L-edge demonstrate that partial oxidation of the Ru(4+) to Ru(5+) occurs upon introducing Ni into the SrRuO(3) structure to form SrRu(0.8)Ni(0.2)O(3). Whilst the diffraction measurements show that SrRu(0.8)Ni(0.2)O(3) is isostructural with SrRuO(3), the Ni doped compound exhibits an unusual first order orthorhombic-cubic phase transition near 670 K as revealed by x-ray diffraction. The Curie temperature in SrRu(0.8)Ni(0.2)O(3) is lower than that found in SrRuO(3) as a consequence of local distortions reducing the p-d hybridization.     

Synthesis and Crystal Structure of 1,3-Bis(p-nitrophenoxy)propane

Abstract  The title compound 1,3-bis(p-nitrophenoxy)propane was synthesized by nucleophilic substitution of p-nitrophenol and 1,3-dibromopropane. Single crystal X-ray diffraction analysis reveals that the molecule in the solid state packs in the monoclinic P2/n space group with crystal cell parameters a = 17.465(5) ?, b = 4.8433(13) ?, c = 17.610(5) ?, β = 100.290(6)o, V = 1465.6(7) ?³, D_calc = 1.442 g/cm⁻³. Two half-molecules are located in the asymmetric unit which are each completed by twofold symmetry making Z = 4, Z′ = 1. Index Abstract  The title compound 1, 3-bis (p-nitrophenoxy) propane was prepared from p-nitrophenol and 1, 3-dibromopropane, crystallized from an ethanolic solution, and the structure was obtained by single crystal X-ray diffraction: monoclinic, P2/n, a = 17.465(5) ?, b = 4.8433(13) ?, c = 17.610(5) ?, β = 100.290(6)°, V = 1465.6(7) ?³.      

Synthesis,swelling properties,and network structure of new stimuli‐responsive poly(N‐acryloyl‐N′‐ethyl piperazine‐co‐N‐isopropylacrylamide) hydrogels

Poly(N‐acryloyl‐N′‐ethyl piperazine‐co‐N‐isopropylacrylamide) hydrogels were prepared by thermal free‐radical copolymerization of N‐acryloyl‐N′‐ethyl piperazine (AcrNEP) and N‐isopropylacrylamide (NIPAM) in solution using N, N′‐methylene bisacrylamide as the crosslinking agent. The gels were responsive to changes in external stimuli such as pH and temperature. The pH and temperature responsive character of the gels was greatly dependent on the monomer content, namely AcrNEP and NIPAM, respectively. The gels swelled in acidic (pH 2) and de‐swelled in basic (pH 10) solutions with a response time of 60 min. With increase in temperature from 23 to 80 °C the swelling of the gels decreased continuously and this effect was different in acidic and basic solutions. The temperature dependence of equilibrium water content of the gels was evaluated by the Gibbs–Helmholtz equation. Detailed analysis of the swelling properties of these new gels in relation to molecular heterogeneity in acidic (pH 2) and basic (pH 10) solutions were performed. Water transport property of the gels was studied gravimetrically. In acidic solution, the diffusion process was non‐Fickian (anomalous) while in basic solution, the diffusion was quasi‐Fickian. The effect was more evident in solution of pH 2 than in pH 10. Various structural parameters of the gels such as number‐average molar mass between crosslink (M_c), the crosslink density (ρ_c), and the mesh size (ξ) were evaluated. The mesh sizes of the hydrogels were between 64 and 783 Å in the swollen state in acidic solution and 20 and 195 Å in the collapsed state in basic solution. The mesh size increased between three to four times during the pH‐dependent swelling process. The amount of unbound water (free water) and bound water of the gels was also evaluated using differential scanning calorimetry. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

N‐(X‐Chlorophenyl)‐4‐hydroxy‐2‐methyl‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide (with X = 2 and 4)

The structures of N‐(2‐chlorophenyl)‐4‐hydroxy‐2‐methyl‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide and N‐(4‐chlorophenyl)‐4‐hydroxy‐2‐methyl‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide, both C₁₆H₁₃ClN₂O₄S, are stabilized by extensive intramolecular hydrogen bonds. The 4‐chloro derivative forms dimeric pairs of molecules lying about inversion centres as a result of intermolecular N—H...O hydrogen bonds, forming 14‐membered rings representing an R₂²(14) motif; the 2‐chloro derivative is devoid of any such intermolecular hydrogen bonds. The heterocyclic thiazine rings in both structures adopt half‐chair conformations.