Catalytic Asymmetric α-Alkylation of Ketones with Unactivated Alkyl Halides.

A catalytic, enantioselective method for direct α-alkylation of ketones with unactivated alkyl halides is realized by employing an α-enolizable ketone in a nickel-catalyzed C(sp3)-C(sp3) cross-coupling reaction. The key to the success is attributed to a unique bimetallic ligand. A variety of acyclic ketones and unactivated alkyl iodides can serve as suitable substrates under mild conditions to generate chiral ketones with α-quaternary carbon stereocenters in high yields with good enantioselectivities. A range of transformations based on the ketone moiety are also demonstrated to show the potential application of this method. Preliminary mechanistic studies support a dinickel-catalyzed cross-coupling mechanism.

Continuous programmable mid-infrared thermal emitter and camouflage based on the phase-change material In3SbTe2.

In3SbTe2 (IST), a new non-volatile phase-change material (PCM), promises highly tunable infrared optical properties and offers a distinct path to the significant modulation of its optical scattering fingerprint, suggesting tremendous applications. In this Letter, we demonstrate and optimize a four-layer emitter based on IST, achieving an ultra-wide average emissivity variation of more than 94% in the middle-infrared region (MIR, 3-5 µm). This remarkable emissivity difference can be further continuously modified by changing the structural composition in terms of the amorphous and crystalline states of the IST layers. Based on this continuous programmable emission, the MIR emission characteristics of marble, maple leaf, and blue polyvinyl chloride are successfully imitated together on a desert background, demonstrating the programmable and multi-level MIR optical camouflage capabilities of IST. This work provides a promising platform for continuously modulating emission characteristics and offers a reference for the subsequent application of programmable optical devices.

Effect of Heat Treatment Temperature on the Spectral Properties of Cu-Ni Coating.

Cu-Ni coatings were prepared on the surface of nickel by electrodeposition method, and Cu-Ni coatings were heat-treated in 25-900 °C. Heat-treated Cu-Ni coatings were characterized with scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX) and X-ray diffraction (XRD) techniques, respectively. Effects of heat treatment temperature on the spectral properties of Cu-Ni coatings were studied. The surface of Cu-Ni coating is composed of the nodules. The nodules of Cu-Ni coating surface become smaller with the increase in heat treatment temperature in 25-600 °C. The nodules of Cu-Ni coating surface become smaller and the dividing line between the nodules becomes more blurred with the increase in heat treatment temperature in 600-900 °C. The contents of copper in Cu-Ni coating decrease from 82.52 at % to 78.30 at % with the increase in heat treatment temperature in the range of 25-900 °C; the contents of nickel in Cu-Ni coating increase from 17.48 at % to 21.70 at % with the increase in heat treatment temperature in the range of 25-900 °C. The crystal structure of Cu-Ni coating is Cu0:8lNi0.19 cubic crystal structure. The crystal structure of the CuO0.81Ni0.19 becomes more complete with the increase in heat treatment temperature in 25- 300 °C. Part of crystal structure of the Cu0.81AlNi0.19 can turn Cu0.8lNi0.19 cubic crystal structure into Cu3.8Ni cubic crystal structure, and is advantageous to Cu3.8Ni (311) and Cu0.81Ni0.19 (311) growth with the increase in heat treatment temperature in 600-900 °C.

Multiple interfaces in self-assembled breath figures.

This feature article describes the multiple interfaces in the breath figure (BF) method toward functional honeycomb films with ordered pores. If a drop of polymer solution in a volatile solvent such as carbon disulphide is placed in a humid environment, evaporative cooling leads to self-assembled arrays of condensed water droplets. After evaporation of the solvent and water, patterned pores can be formed. During this BF process, the interfaces between the solution and the substrate, the solution and water droplets, and the film surface and air play extremely important roles in determining both the structures and functions of the honeycomb films. Progress in the BF method is reviewed by emphasizing the roles of the interfacial interactions. The applications of hierarchical and functional honeycomb films in separation, biocatalysis, biosensing, templating, stimuli-responsive surfaces and adhesive surfaces are also discussed.

Polystyrenes with hydrophilic end groups: synthesis, characterization, and effects on the self-assembly of breath figure arrays.

We report the synthesis and characterization of a series of hydroxyl-end-functionalized polystyrenes (PS-OH) and the formation of patterned porous films. The polymers were synthesized by chain end reaction of polystyrene having a bromide end group (PS-Br) with hydramines including ethanolamine, diethanol amine, 2-amino-1,3-propanediol, and 2-(2-aminoethoxy) ethanol. The polymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and differential scanning calorimetry (DSC). It was found that the end groups can influence the glass transition temperature (T(g)) of the polystyrenes. The polymers with different end groups were then used to prepare honeycomb-patterned porous films by the breath figure method. Results reveal that the subtle chain-end modification leads to a dramatic change in the morphology of the films. Honeycomb films with large area ordered structure can be easily prepared from PS-OH. Effects of the end groups as well as blending PS-OH with PS-Br on the surface pore diameter, pore center distance, and the hierarchical structure were studied in detail. As supported by the results of polymer hydrophilicity, in situ observation of the film formation process, as well as the chain mobility, the film structure is supposed to be mainly determined by the precipitation of polystyrene at the solution/water droplet interface and the interfacial activity enhanced by the end groups.