Tuning the surface hydrophobicity of polymer/nanoparticle composite films in the Wenzel regime by composition

Surface hydrophobicity of composite films containing polymer and nanoparticles has been studied as a function of composition. We show that the hydrophobicity can be tuned by adjusting the amount of particles in the two-component system. A sharp transition from a polymer-rich surface to a nanoparticles-rich surface was observed with increasing mass fraction of particles in spin-coated thin films. Water drops on the films did not slide down even at tilt angles of 90 degrees . Contact angle hysteresis increased with the mass fraction of particles indicating that the surface roughness increased as the surfaces remained in the Wenzel regime. Contact angle hysteresis data were quantitatively consistent with predictions of a recent theory.     

Broadening and shift of lines of the principal series of neutral lithium atom produced by collision with helium and argon

Collision broadening and shift produced by argon and helium have been determined in absorption at low pressures for lines of the main series of neutral lithium. The experimental profiles were corrected for instrumental distortions. The actual line profile is well represented by a Voigt function. The collision-broadening and shift rates were derived from the measurements. The experimental data were analyzed by using the impact theory and the Lennard-Jones potential. Interatomic potential constants were thus determined for an excited state Li(I) atom interacting with a ground state Ar or He atom. We have compared experimentally-determined potentials with theoretical “pseudo-potential” curves.     

Fast ground state manipulation of neutral atoms in microscopic optical traps

We demonstrate Rabi flopping at MHz rates between ground hyperfine states of neutral 87Rb atoms that are trapped in two micron sized optical traps. Using tightly focused laser beams we demonstrate high fidelity, site specific Rabi rotations with cross talk on neighboring sites separated by 8 microm at the level of 10(-3). Ramsey spectroscopy is used to measure a dephasing time of 870 micros, which is approximately 5000 longer than the time for a pi/2 pulse.     

Pore-Scale Analysis of NAPL Blob Dissolution and Mobilization in Porous Media

A pore-scale analysis of nonaqueous phase liquid (NAPL) blob dissolution and mobilization in porous media was presented. Dissolution kinetics of residual NAPLs in an otherwise water-saturated porous medium was investigated by conducting micromodel experiments. Changes in residual NAPL volume were measured from recorded video images to calculate the mass transfer coefficient, K and the lumped mass transfer rate coefficient, k. The morphological characteristics of the blobs such as specific and intrinsic area were found to be independent of water flow rate except at NAPL saturations below 2%. Dissolution process was also investigated by separating the mass transfer into zones of mobile and immobile water. The fractions of total residual NAPL perimeters in contact with mobile water and immobile water were measured and their relationship to the mass transfer coefficient was discussed. In general, residual NAPLs are removed by dissolution and mobilization. Although these two mechanisms were studied individually by others, their simultaneous occurrence was not considered. Therefore, in this study, mobilization of dissolving NAPL blobs was investigated by an analysis of the forces acting on a trapped NAPL blob. A dimensional analysis was performed to quantify the residual blob mobilization in terms of dimensionless Capillary number (Ca _I). If Ca _I is equal to or greater than the trapping number defined as , then blob mobilization is expected.     

On the Evaluation Overlap Integrals with the Same and Different Screening Parameters Over Slater Type Orbitals via the Fourier-Transform Method

In this paper, derivation of analytical expressions for overlap integrals with the same and different screening parameters of Slater type orbitals (STOs) via the Fourier-transform method is presented. Consequently, it is relatively easy to express the Fourier integral representations of the overlap integrals with same and different screening parameters mentioned as finite sums of Gegenbauer, Gaunt, binomial coefficients, and STOs.     

Synthesis and Spectroscopic Properties of Carbazole-Oxadiazoles

Four new carbazole-oxadiazole derivatives (3a-b, 6a-b) were prepared from the reaction of aromatic aldehydes and carbohydrazides which were synthesized from carbazole aldehydes namely 9-hexyl-9H-carbazole-3-carbaldehyde 1 and 4-(9H-carbazole-9-yl)benzaldehyde 4 and acid hydrazides. The structures of the new derivatives were confirmed by ¹H-NMR and FT-IR. The optical properties such as maximum absorption and emission wavelengths (λ; nm), molar extinction coefficients (ε; cm^?1 M^?1), Stoke’s shifts (ΔλST; nm) and quantum yields (?F), of the carbazole-oxadiazole derivatives were declared in dichloromethane, toluene and tetrahydrofuran solutions.     

Noninvasive functionalization of polymers of intrinsic microporosity for enhanced CO(2) capture

Modifying sorbents for the purpose of improving carbon dioxide capture often results in the loss of surface area or accessible pores, or both. We report the first noninvasive functionalization of the polymers of intrinsic microporosity (PIMs) where inclusion of the amidoxime functionality in PIM-1 increases carbon dioxide capacity up to 17% and micropore surface area by 20% without losing its film forming ability.     

Synthesis of Poly(tartar amides) as Bio‐Inspired Antifreeze Additives

Summary: Multifunctional poly(tartar amides) have been synthesized and used as bio‐inspired antifreeze additives. It is shown that these polymers strongly interfere with the crystallization process of water in comparison to commercially available commodity polymers. While the addition of the poly(tartar amides) results in minor freezing point depression, as is shown by differential scanning calorimetry, a strong change in the ice crystal morphology is evident. Wide‐angle X‐ray scattering and optical microscopy indicate that the hexagonal structure of undisturbed ice‐crystals is oriented and partly deformed.

Light microscopy image of ice crystals at 223 K after a freezing assay with poly(tartar amides) shown at a polymer concentration of 2 wt.‐%.