Polyelectrolyte Configuration of Low Molecular Weight Sodium Amylose Xanthate in Aqueous and Salt Solutions

The polyelectrolyte chain configuration of low molecular weight sodium amylose xanthate (NaAX) in aqueous and salt solutions has been studied by viscometry and light scattering. The viscometric results in aqueous solution have been found to be in accordance with the Fuoss's modified equation. The intrinsic viscosities of NaAX in salt solutions from 0.00125 to 0.25 M NaCl have been determined and the expansion factor a at each ionic strength has been determined. The dependence of a on ionic strength has been studied according to the theories of Hermans and Overbeek, Flory, etc. But though qualitative agreement between experimental and theoretical results has been found, quantitative agreement was far from expectations. The frictional coefficient per monomer unit | has been calculated from the relationship of Kirkwood and Riseman. The NaAX macromolecule has been found to have the polydispersed random coil chain configuration in 0.25 M NaCl. Some macromolecular configurational parameters such as effective bond length b, Kuhn-Kuhn equivalent chain length A_m, and steric factor α has been determined.     

Comparative Studies on Thermomechanical Behavior of Veriflex®, a Shape Memory Polymer,for a Low Strain (ϵm = 70%): Laser Experiments

An interesting comparative case study on thermomechanical cycles including programming, cooling, unloading and heating to trigger the 1WE was done using Veriflex® at 62°C (T < T_g close to and below 5°C of T_g) and also at 72°C (T > T_g, close to and above 5°C of T_g) for slightly low strains (?_m = 70%) and the recovery time of 10 min. Accumulation of strain was estimated during the thermomechanical treatments for using both 70% strains at 62°C (T < T_g), as well as at 72°C (T > T_g). Recovery ratios for 70% strains at 62°C (T < T_g), as well as for 72°C (T > T_g) were also estimated. It turns out that programming, cooling, unloading and heating to trigger the 1WE causes an increase of irreversible strain and is associated with a corresponding decrease of the intensity of the 1WE, in particular, during the first thermomechanical cycles. A LSCM (Laser Scanning Confocal Microscopic) study shows very little change in surface structure which evolved during cycling up to 70% strains at 72°C (T > T_g).     

Approximate controllability for linearized compressible barotropic Navier–Stokes system in one and two dimensions

In this paper we consider compressible barotropic Navier–Stokes equations in one and two dimensions linearized around a constant steady state with Dirichlet boundary conditions. We explore the controllability of this linearized system using a control only for the velocity equation. We prove that the system with homogeneous Dirichlet boundary conditions, is approximately controllable by a localized interior control when time is sufficiently large.     

The use of triethanolamine ammonium salts as catalysts for the addition of carbon dioxide to epoxides

Russian Chemical Bulletin - Ammonium derivatives of triethanolamine have been effectively used as catalysts for the addition of CO2 to epoxides. The iodine additive was found to exert a positive...     

Initial Carbon−Carbon Bond Formation during the Early Stages of Methane Dehydroaromatization

Methane dehydroaromatization (MDA) is among the most challenging processes in catalysis science owing to the inherent harsh reaction conditions and fast catalyst deactivation. To improve this process, understanding the mechanism of the initial C?C bond formation is essential. However, consensus about the actual reaction mechanism is still to be achieved. In this work, using advanced magic‐angle spinning (MAS) solid‐state NMR spectroscopy, we study in detail the early stages of the reaction over a well‐dispersed Mo/H‐ZSM‐5 catalyst. Simultaneous detection of acetylene (i.e., presumably the direct C?C bond‐forming product from methane), methylidene, allenes, acetal, and surface‐formate species, along with the typical olefinic/aromatic species, allow us to conclude the existence of at least two independent C?H activation pathways. Moreover, this study emphasizes the significance of mobility‐dependent host–guest chemistry between an inorganic zeolite and its trapped organic species during heterogeneous catalysis.     

Azido derivatives of dinuclear copper(II) and 1D polynuclear nickel(II) complexes containing an unsymmetrical bidentate amine: synthesis,crystalline architecture,and magnetic behavior

Transition Metal Chemistry - Dinuclear copper(II) complex [Cu2(L)2(μ2-1,1-N3)2(N3)2] (1) with double μ1,1-azido bridges and polynuclear nickel(II) complex...     

Supersymmetric Integrable Systems in (2 + 1) Dimensions and Their Backlund Transformation

Nonlinear integrable systems in (2 + 1)dimensions which are supersymmetric are generated in twodifferent ways. In one approach the homogeneous spacesof super-Lie algebra are used, and in the other we use a different technique of extending thedimension of the system. The two sets of equations turnout to be different. The methodologies ofDarbux–Backlund transformation and gaugetransformation are used to generate the Backlund transformations ofthese equations. An important result of our analysis isthe existence of purely fermionic nonlinear systems in(2 + 1) dimensions.     

Organocatalytic Michael addition of aldehydes to a β-silylmethylene malonate to form intermediates for the enantioselective synthesis of hydroxylated valerolactones and piperidines

The direct Michael addition of enolizable aldehydes to dimethyl(phenyl)silylmethylene malonate was catalysed by an (S)-diphenylprolinol trimethylsilyl ether/acetic acid combination. The adducts were formed in good yield, high diastereoselectivity and excellent enantioselectivity. Chiral valerolactone and piperidine skeletons embedded with a silyl and other functionalities have been made out of the adducts. A total synthesis (+)-simplactone B has been achieved from one of the adducts.