Concentration, temperature, and salt-induced micellization of a triblock copolymer Pluronic L64 in aqueous media

The effect of copolymer concentration, temperature, and sodium halides (NaI, NaBr, NaCl, and NaF) on micellization and micellar properties of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO13PO30EO13), was examined by different methods such as dye spectral change, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), small angle neutron scattering (SANS), dynamic light scattering (DLS), viscosity, and cloud point (CP). Temperature/polymer concentration/salt dependent aggregation behavior of L64 was observed. The data on critical micelle concentration (CMC), critical micelle temperature (CMT), (CP), micelle size, and shape are reported. The Fourier transform infrared (FTIR) showed temperature dependent changes in C-O-C stretching variation band towards higher wave numbers and broadening of band width during the micellization process; this was attributed to increase in proportion of the anhydrous methyl groups, while the proportion of the hydrated methyl groups was decreased. Differential scanning calorimetry (DSC) provides CMTs and CPs from the same experiment. CMC values derived from dye spectral change, decrease significantly with the addition of salt. The increases in salt/copolymer concentration lower the onset temperature of micellization (CMT). Halide anions influence both CMT and CP in the order of F- > Cl- > Br- > I- when total salt and copolymer concentration kept constant. SANS results show the increase of inter-micellar interaction due to the increase in temperature/salt concentration; this is supported by viscosity data.     

A highly efficient stereoselective synthesis of (Z)- and (E)-allyl iodides from Baylis-Hillman adducts

A highly efficient synthesis of (Z)- and (E)-allyl iodides has been accomplished by treatment of Baylis-Hillman adducts with iodine and triphenylphosphine in methylene chloride at room temperature. The method is associated with mild reaction conditions, high yields and excellent stereoselectivity.     

Rhodium(III) iodide hydrate catalyzed three-component coupling reaction: synthesis of α-aminonitriles from aldehydes, amines, and trimethylsilyl cyanide

Aryl imines formed from aldehydes and amines undergo smoothly in situ nucleophilic addition with trimethylsilyl cyanide (TMSCN) in the presence of catalytic amount of hydrated rhodium(III) iodide to afford the corresponding α-aminonitriles in excellent yield. The low catalytic loading (2 mol %), mild experimental conditions, and short reaction time (mostly within 13 min) represent the key features of this novel catalytic system.     

Morphological orders of spherulitic crystal textures in Belousov-Zhabotinsky-type oscillatory reaction system

The morphological orders of spherulitic crystal patterns in a Belousov-Zhabotinsky-type oscillatory reaction system were studied. The experiments showed that the morphology of crystal patterns were highly dependent on the reaction temperature. The reaction was initially carried out at 30 °C, leading to the growth of multi-centred spherulitic patterns. The single-centred spherulitic patterns with fairly large crystal fibrils were obtained at 35°C. A number of undersized crystal assemblies with fractal geometry were also investigated at 25°C. The gross morphology of the crystal patterns was examined using optical microscopy and a scanning electron microscope which revealed the fibrous organisations. A particle-mediated self-assembly scheme was proposed for the growth of the spherulitic patterns. The insight into the nucleation mechanism, growth behaviour, and morphological orders of the growing patterns is discussed in detail. The crystal phases, ordering of textures, and composition of the crystals were characterised by thermal and X-ray diffraction techniques.     

On some geometric optimization problems in layered manufacturing

Efficient geometric algorithms are given for optimization problems arising in layered manufacturing, where a 3D object is built by slicing its CAD model into layers and manufacturing the layers successively. The problems considered include minimizing the stair-step error on the surfaces of the manufactured object under various formulations, minimizing the volume of the so-called support structures used, and minimizing the contact area between the supports and the manufactured object—all of which are factors that affect the speed and accuracy of the process. The stair-step minimization algorithm is valid for any polyhedron, while the support minimization algorithms are applicable only to convex polyhedra. The techniques used to obtain these results include construction and searching of certain arrangements on the sphere, 3D convex hulls, halfplane range searching, and constrained optimization.     

INFLUENCE OF RIGID BOUNDARY ON THE LOVE WAVE PROPAGATION IN ELASTIC LAYER WITH VOID PORES

In this paper, a mathematical model for Love wave propagation in a porous elastic layer under a rigid boundary resting over a poro-elastic half-space has been developed. The study shows that such a medium transmits two types of Love waves. The first front depends on the change in volume fraction of the pores whereas the second front depends upon the modulus of rigidity of the elastic matrix of the medium and is the same as the Love wave in an elastic layer over an elastic half-space. It is observed that the first front is many times faster than the shear wave in the medium with void pores due to the change in the volume fraction of the pores and is significant.     

Reflection and transmission of SH-waves at a corrugated interface between two semi-infinite anisotropic magnetoelastic half-spaces

An analysis has been carried out for reflection and transmission of a plane SH-wave incident at a corrugated interface between two anisotropic magnetoelastic half-spaces. Rayleigh’s method of approximation is applied to derive the reflection and transmission coefficients for first order approximation of corrugation. The expressions for reflection and transmission coefficients for first order approximation of corrugation are obtained in closed form for a special type of interface. It is found that these coefficients are proportional to the amplitude of corrugation and are functions of magnetoelastic properties of materials of the half-spaces as well as the angle of incidence. Special cases are deduced for anisotropic and isotropic materials for particular case of corrugation. Numerical computations are performed for a specific model of two different anisotropic magnetoelastic media. The effects of anisotropic magnetoelastic coupling parameter, the angle at which wave crosses the magnetic field, frequency factor, wave length of corrugation, and the amplitude of corrugation are shown through figures.     

A practical and sustainable two-component Minisci alkylation via photo-induced EDA-complex activation

An operationally simple, open-air, and efficient light-mediated Minisci C–H alkylation method is described, based on the formation of an electron donor–acceptor (EDA) complex between nitrogen-containing heterocycles and redox-active esters. In contrast to previously reported protocols, this method does not require a photocatalyst, an external single electron transfer agent, or an oxidant additive. Achieved under mildly acidic and open-air conditions, the reaction incorporates primary-, secondary-, and tertiary radicals, including bicyclo[1.1.1]pentyl (BCP) radicals, along with various heterocycles to generate Minisci alkylation products in moderate to good yields. Additionally, the method is exploited to generate a stereo-enriched, hetereoaryl-substituted carbohydrate.

An operationally simple, open-air, and efficient light-mediated Minisci C–H alkylation method is described, based on the formation of an electron donor–acceptor (EDA) complex between nitrogen-containing heterocycles and redox-active esters.     

Carbene‐Catalyzed Dynamic Kinetic Resolution and Asymmetric Acylation of Hydroxyphthalides and Related Natural Products

A catalytic dynamic kinetic resolution and asymmetric acylation reaction of hydroxyphthalides is developed. The reaction involves formation of a carbene catalyst derived chiral acyl azolium intermediate that effectively differentiates the two enantiomers of racemic hydroxyphthalides. The method allows quick access to enantiomerically enriched phthalidyl esters with proven applications in medicine. It also enables asymmetric modification of natural products and other functional molecules that contain acetal/ketal groups, such as corollosporine and fimbricalyxlactone C.     

Carbene‐Catalyzed Enantioselective Aldol Reaction: Post‐Aldol Stereochemistry Control and Formation of Quaternary Stereogenic Centers

The dominated approaches for asymmetric aldol reactions have primarily focused on the aldol carbon–carbon bond‐forming events. Here we postulate and develop a new catalytic strategy that seeks to modulate the reaction thermodynamics and control the product enantioselectivities via post‐aldol processes. Specifically, an NHC catalyst is used to activate a masked enolate substrate (vinyl carbonate) to promote the aldol reaction in a non‐enantioselective manner. This reversible aldol event is subsequently followed by an enantioselective acylative kinetic resolution that is mediated by the same (chiral) NHC catalyst without introducing any additional substance. This post‐aldol process takes care of the enantioselectivity issues and drives the otherwise reversible aldol reaction toward a complete conversion. The acylated aldol products bearing quaternary/tetrasubstituted carbon stereogenic centers are formed in good yields and high optical purities.