Kinetics of Polymerization of Methyl Methacrylate initiated by AIBN in the Presence of Acetophenone

The present investigation aims at estimating the retarding effect of acetophenone in the polymerization of methyl methacrylate initiated by α,α' -azobisisobutyronitrile in the temperature range of 50 to 80°C. The results are interpreted in terms of Tüdös kinetic parameter (β). The effects of varying concentrations of substrate, monomer, initiator, and salts have been investigated. A suitable reaction scheme and rate expression have been suggested on the basis of the experimental findings, and another kinetic parameter (K) to represent the reactivity of acetophenones toward the polymer radical has been obtained graphically.     

Synthesis and Study of Polymeric Ultraviolet Absorbers. II

Polymeric UV absorbers have been prepared by free-radical solution copolymerization at 75°C of methyl methacrylate and 2-hydroxy-4-methacryloyloxybenzophenone monomers at low conversion (around 10%). The composition of the copolymers was determined by UV, IR, and NMR studies. The molecular weight was estimated by GPC. The reactivity ratios were determined by several methods. Viscosity was used to study the effect of copolymer composition and solvents. The copolymers were also analyzed by TGA and DSC, and DSC was used to study the effect of copolymer composition on T_g.     

Biphasic kinetic investigations on the evaluation of non-salt forming reductants for Pu(IV) stripping from tributyl phosphate and N,N-dihexyl octanamide solutions in n-dodecane

The relative stability of different oxidation states of actinide elements is influenced by the nature of complexes formed and redox equilibria in aqueous/non-aqueous solutions. The reduction/stripping studies on Pu(IV) ions from loaded organic phases of 1.1 M tributyl phosphate and of 1.1 M N,N-dihexyl octanamide in n-dodecane were studied using organic soluble tert-butyl hydroquinone (TBH) and aqueous soluble reductants like acetaldoxime (AX) and hydroxyurea (HU). These studies were carried out as a function of reductant and nitric acid concentration (0.5–4 M HNO₃) and of time. The changes in Pu oxidation states were followed by spectrophotometry for TBH and by distribution ratio values for AX and HU as reductants. Spectrophotometric investigations using TBH as reductant showed that it was desirable to strip Pu(III) formed after reduction of Pu(IV) in the organic phase, which may otherwise be reconverted to extractable Pu(IV) by in situ generated HNO₂ from oxidative degradation of TBH to tert-butyl quinone. Similarly, the biphasic reduction/stripping of Pu(IV) using AX and HU as reductant rate was affected adversely with increased aqueous phase acidity. This data will help in the accurate simulation of Pu separation processes using these reductants in mixer-settlers/pulsed columns or centrifugal contactors.     

A critical analysis of the effect of crosslinking on the linear viscoelastic behavior of styrene–butadiene rubber and other elastomers

The linear viscoelastic behavior in dynamic shear and tensile creep at temperatures from −30 to 70 °C is measured for an styrene–butadiene rubber (SBR) elastomer cured with dicumyl peroxide to crosslinking densities between 0 and 23.5 × 10⁻⁵ mol/cm³. The G′, G″, and tan δ isotherms are analyzed by time–temperature superposition (TTS), where the tan δ master curves are consistent with those of Mancke and Ferry. However, to achieve the TTS in the lightly crosslinked SBR systems, an anomalous vertical shift is required in the narrow temperature region from 10 to 30 °C. The vertical shift factor in this temperature region is not the standard from rubber elasticity. No anomalous behavior is detected in the equilibrium modulus, which is a linear function of temperature in accordance with the classical theory of rubber elasticity. In contrast to SBR, standard vertical shifts are required to effect TTS for uncrosslinked polybutadiene and an ethylene propylene diene monomer elastomer. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Experimental and Theoretical Studies on Synthesized Compounds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Imidazole derivatives, namely, 1-((1-(piperazinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (PBIP), and 1-((1-(morpholinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (MBIP) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. It was found that the inhibition efficiency of both the inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. The inhibitors, PBIP and MBIP, show corrosion inhibition efficiency of 92.6% and 91.4% at 300 ppm concentration, respectively, at 303 K. Polarization studies showed that both the studied inhibitors were of mixed type in nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed for surface study of uninhibited and inhibited mild steel samples. The semi-empirical AM1 method was employed for theoretical calculations.     

Catalytic Sc(OTf)3 mediated direct asymmetric aldol reaction of (−)-menthyl isothiocyanatoacetate with aldehydes by using (−)-menthol as chiral auxiliary

This method involves the direct asymmetric aldol reaction of (−)-menthyl isothiocyanatoacetate 5 with a variety of substituted aromatic aldehydes, which offers a convenient method for the synthesis of intermediate containing biologically relevant α-amino β-hydroxyl groups in oxazolidine ring. In this methodology, the products show remarkable diastereoselectivity using Sc(OTf)₃ as a catalyst and easily accessible (−)-menthol as a chiral auxiliary. This approach includes some important aspects such as mild reaction conditions, high yields, and excellent diastereoselectivity with a number of substituted aromatic aldehydes. The optimization and effect of different catalysts were studied at different reaction conditions and it is found that Sc(OTf)₃ shows excellent diastereoselectivity at −45°C.     

Synthesis and metal complexation studies of [2n]thiacalix[m]arene[m]pyrazine

Novel [2_n]thiacalixarenepyrazine and [2_n]thiacalixarenetriazine systems were synthesised by one-pot S_NAr reactions. A screening of the metal-complexing ability of [2₆]hexathiacalix[3]arene[3]pyrazine revealed its affinity for Cu^I, Cu^II and Ag^I metal salts.     

Vesicle Structures from Bolaamphiphilic Biosurfactants: Experimental and Molecular Dynamics Simulation Studies on the Effect of Unsaturation on Sophorolipid Self‐Assemblies

The formation of giant‐vesicle‐like structures by self‐assembling linolenic acid sophorolipid (LNSL) molecules is revealed. Sophorolipids belong to the class of bolaamphiphilic glycolipid biosurfactants. Interestingly, the number of double bonds present in the hydrophobic core of sophorolipids is seen to have a great influence on the type of self‐assembled structures formed. Dye encapsulation results establish the presence of an aqueous compartment inside the LNSL vesicles. Molecular dynamics simulation (MD) studies suggest the existence of two possible conformations of LNSLs inside the self‐assembled structures and that LNSL molecules arrange in layered structures.