Unusually stable molecular capsule formation of a tetraphenyleneurea cavitand

An unusually stable molecular capsule was formed by heating phenyleneurea-spanned resorcinarene cavitand with 4-methyl-N-p-tolylbenzamide. The molecular capsule behaved as a discrete molecular entity showing a cylindrical D(4d) structure and showed no guest exchange in toluene-d(8) even at 100 degrees C. [structure: see text]     

Hydrodynamic microfabrication via"on the fly" photopolymerization of microscale fibers and tubes

A microfluidic apparatus capable of creating continuous microscale cylindrical polymeric structures has been developed. This system is able to produce microstructures (e.g. fibers, tubes) by employing 3D multiple stream laminar flow and "on the fly"in-situ photopolymerization. The details of the fabrication process and the characterization of the produced microfibers are described. The apparatus is constructed by merging pulled glass pipettes with PDMS molding technology and used to manufacture the fibers and tubes. By controlling the sample and sheath volume flow rates, the dimensions of the microstructures produced can be altered without re-tooling. The fiber properties including elasticity, stimuli responsiveness, and biosensing are characterized. Responsive woven fabric and biosensing fibers are demonstrated. The fabrication process is simple, cost effective and flexible in materials, geometries, and scales.     

Brownian Dynamics, Molecular Dynamics, and Monte Carlo modeling of colloidal systems

This paper serves as an introductory review of Brownian Dynamics (BD), Molecular Dynamics (MD), and Monte Carlo (MC) modeling techniques. These three simulation methods have proven to be exceptional investigative solutions for probing discrete molecular, ionic, and colloidal motions at their basic microscopic levels. The review offers a general study of the classical theories and algorithms that are foundational to Brownian Dynamics, Molecular Dynamics, and Monte Carlo simulations. Important topics of interest include fundamental theories that govern Brownian motion, the Langevin equation, the Verlet algorithm, and the Metropolis method. Brownian Dynamics demonstrates advantages over Molecular Dynamics as pertaining to the issue of time-scale separation. Monte Carlo methods exhibit strengths in terms of ease of implementation. Hybrid techniques that combine these methods and draw from these efficacies are also presented. With their rigorous microscopic approach, Brownian Dynamics, Molecular Dynamics, and Monte Carlo methods prove to be especially viable modeling methods for problems with challenging complexities such as high-level particle concentration and multiple particle interactions. These methods hold promising potential for effective modeling of transport in colloidal systems.     

Enantioselective synthesis of allenyl carbinols by the CBS reduction in nitroethane: dramatic solvent effect for reactivity and enantioselectivity

Dramatic solvent effect of nitroethane was observed in the catalytic asymmetric reductions of allenyl ketones and alpha,beta-ynones using the oxazaborolidine cayalyst to yield the corresponding alcohols in high levels of enantioselectivity.     

Size-selective synthesis of gold and platinum nanoparticles using novel thiol-functionalized ionic liquids

One-phase synthesis of gold and platinum nanoparticles using new thiol-functionalized ionic liquids (TFILs) is described for the first time. TFILs as stabilizing agents for gold and platinum nanoparticles were designed to have thiol groups on either the cation or anion and symmetrical or unsymmetrical positions only in the cation. Transmission electron microscopy, electron diffraction, and NMR were used for the characterization of nanoparticles. The metal nanoparticles formed using TFILs are crystalline structures with face-centered cubic packing arrangements and have small sizes (the average diameters are 3.5, 3.1, and 2.0 nm for Au and 3.2, 2.2, and 2.0 nm for Pt, respectively) and uniform distributions (the standard deviations are 0.7, 0.5, and 0.1 nm for Au and 1.1, 0.2, and 0.1 for Pt, respectively). It is believed that the nanoparticle size and distribution depend on the number and position of thiol groups in the IL.     

Pattern generation of biological ligands on a biodegradable poly(glycolic acid) film

The micropatterns of biological ligands (biotin and RGD peptides) were generated on a flat surface of biodegradable polymer, poly(glycolic acid) (PGA). The immobilization of biological ligands onto the surface of biodegradable polymers (especially aliphatic polyesters) is usually hampered by the absence of functionalizable groups on the polymer backbone. We demonstrate herein that PGA polymer films were modified by surface hydrolysis to introduce carboxylic acid groups on the film surfaces, which were subsequently used for patterning amine-terminated ligands by microcontact printing. Fluorescence microscopy was used to verify the pattern of biotin on the surface of the PGA films after complexation with fluorescein-conjugated streptavidin. In addition, the cellular micropatterns were obtained from micropatterns of RGD peptides on the surface-hydrolyzed PGA films.     

Pore morphologies in disordered nanoporous thin films

Materials with nanometer size heterogeneities are commonplace in the chemical and biological sciences (e.g, polymer blends, microemulsions, gels) and often exhibit complex morphologies. Although this morphology has a dramatic effect on the materials' properties, it is often difficult to accurately characterize. We describe a method, using small-angle X-ray scattering data, of generating representative three-dimensional morphologies of isotropic two-phase materials where the morphology is disordered, and we apply this to thin films containing nanometer sized pores with a range of porosities (4-44%). These representations provide a visualization of the pore morphology, give the pore size scale and extent of interconnection, and permit the determination of the transitions from closed pore to interconnected pores to bicontinuous morphology.     

Universal occurrence of soot superaggregates with a fractal dimension of 2.6 in heavily sooting laminar diffusion flames

Using small-angle light scattering we show that a new phase of soot with size ca. 10 microm and a fractal dimension of D approximately equal to 2.6 exists in laminar diffusion flames for a wide range of heavily sooting fuels. This new phase appears to be a supramicrometer extension of the well-known submicrometer, D approximately equal to 1.8 phase of soot formed via diffusion-limited cluster aggregation (DLCA). The occurrence of this new soot phase correlates with an empirical sooting index for fuels. This supports a creation scenario in which these supramicrometer aggregates are created via a percolation of the submicrometer, D approximately equal to 1.8 aggregates.     

Unexpected Direction of Iodocyclization of 3-Allylthio-5-phenyl-4H-1,2,4-triazole

The reaction of 3-allylthio-5-phenyl-4H-1,2,4-triazole with iodine to give a mixture of 5,6-dihydro-5-iodomethyl-3-phenyl[1,3]thiazolo[2,3-c][1,2,4]triazole, 6,7-dihydro-6-iodo-3-phenyl-5H-[1,2,4]triazolo[3,4-b][1,3]thiazine, 5,6-dihydro-6-iodomethyl-2-phenyl[1,3]thiazolo[3,2-b][1,2,4]triazole, and 6,7-dihydro-6-iodo-2-phenyl-5H-[1,2,4]triazolo[5,1-b][1,3]thiazine has been studied. The structure of the products obtained was established using ¹H NMR spectroscopy of their dehydriodination products.