Living polymerization of 1,3-butadiene catalyzed by half-titanocene complex bearing dibenzhydryl-substituted aryloxide ligand

Half-titanocene complexes bearing dibenzhydryl-substituted aryloxide ligands(2a-2d) were prepared. Among them, 2c adopted a three-legged distorted tetrahedral geometry evidenced by X-ray crystallography. The poly-1,3-butadiene with high molecular weight and narrow molecular weight distribution was obtained by using these complexes as the catalysts activated with methylaluminoxane(MAO). The catalytic activities of the complexes depended on their structures. The Ti―O―C bond in the complexes with large angle afforded them with higher activity, while Cp*-based complexes exhibited lower activities than the Cp-based analogues. The activity of complex increased with increasing the polymerization temperature while the selectivity remained no change, indicating the high thermal stability. Furthermore, the polymerization of 1,3-butadiene catalyzed by 2a/MAO at 0 °C has been found in a living fashion.     

Preparation of chitosan/N-doped graphene natively grown on hierarchical porous carbon nanocomposite as a sensor platform for determination of tartrazine

In this work,the chitosan and N-doped graphene natively grown on hierarchical porous carbon(N-PC-G/CS) nanocomposite was obtained by ultrasonic method,as a novel sensor platform for determination of tartrazine(TT).The nanocomposite as prepared had well dispersivity in water and excellent conductivity.The N-PC-G/CS nanocomposite was characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),nitrogen adsorption-desorption,fourier transform infrared(FTIR) and electrochemical impedance spectroscopy(EIS).The application of N-PC-G/CS for determination of tartrazine(TT) was investigated by chronocoulometry(CC),cyclic voltammetry(CV) and differential pulse voltammetry(DPV).Under optimized conditions,the sensor displayed a sensitive response to TT within a wide concentration range of 0.05-15.0 μmol/L,the detection limits is 0.036 μmol/L(S/N = 3).Furthermore,this nanocomposite could be efficiently applied for determination of TT in soft drink samples.     

Synthesis,characterization and effects of arm number on properties of amphiphilic polyurethanes as drug delivery carriers

Amphiphilic polyurethanes based on methoxy poly(ethylene glycol) (mPEG) and poly(?-caprolactone) diol (PCL) with different arm numbers such as two, three and four were successfully synthesized. Their structures were confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR) and gel permeation chromatography (GPC). The effects of arm number on properties of amphiphilic polyurethanes were studied. Pyrene fluorescence probe technique and dynamic light scattering (DLS) analyses showed that the CMC value and the micellar size of the resultant amphiphilic polyurethanes decreased and the micellar stability against dilution enhanced with increasing the arm number of polyurethane. Using indometacin (IMC) as a model drug, the results indicated that the drug loading capacity and in vitro drug sustained release effect of polyurethane with four arms were better than those of polyurethanes with two and three arms.     

Observation of the mica surface by atomic force microscopy

Freshly cleaved mica and a mica surface treated with pure water and dilute-salt solution have been investigated by Atomic Force Microscopy (AFM). On the bare mica surface (after repeated scanning), small dots and islands were observed. The disappearance of these dots and islands has also been captured by AFM. We believe these structures to be condensed water. The water meniscus between AFM tip and mica surface is considered as the source of this water structure. On the mica surface treated with pure water and dilute-salt solution, network structures are frequently observed by AFM.     

Effect of wall temperature on hypersonic turbulent boundary layer

Turbulent boundary layers at Mach 4.9 with the ratio of wall temperature to recovery temperature from 0.5 to 1.5 are investigated by means of direct numerical simulation. Various fundamental properties relevant to the influence of wall temperature on Morkovin’s scaling, standard and modified strong Reynolds analogies, and coherent vortical structures have been studied. It is identified that the scaling relations proposed for cool and adiabatic wall conditions, such as Morkovin’s scaling and the modified strong Reynolds analogy, are also applicable for hot wall condition. Moreover, the relation between the density and temperature fluctuations under the second-order approximation is derived and verified to provide a reliable prediction. Based on the analysis of coherent vortical structures, it is found that the orientation of vortex core can be quantitatively determined by means of the vector with its direction and modulus using the local strain direction and the imaginary part of the eigenvalue of velocity gradient tensor, respectively. As the increase of wall temperature, the spanwise distance between the two legs of hairpin vortex increases, and the mean swirling strength and the angle of vortical structure with respect to the wall plane also increase in the inner layer. The statistical properties relevant to vortical structures are nearly insensitive to the wall temperature in the outer layer.     

Comb-Channels of Left–Right-Handed Circular Polarizations from Coupled Resonators

In order to obtain multi-channels of left–right-handed circular polarizations, we design a structure with coupled magnetic resonators and study its transmission properties using the tight-binding model and the 4×4 transfer matrix method. The incidence of a linearly polarized light can be split into two groups of resonant peaks. One group corresponds left-handed circular polarization and the other group corresponds to right-handed circular polarization. By properly adjusted magnetization, the two group can be merged into one group, in which the channels of left-handed circular polarization and right-handed circular polarization are alternately arranged in the transmission spectrum. Thus, we can obtain the comb-channels of left–right-handed circular polarizations.     

K(+)-recognition capsules with squirting release mechanisms

K(+)-recognition capsules are developed to translate K(+)-recognition into a squirting release function. Upon recognition of K(+), the capsules shrink rapidly and squirt out encapsulated oil cores due to the cooperative interaction of host-guest complexation and phase transition in capsule membranes. The capsules provide a promising model for K(+)-recognition smart functional systems.     

Enhanced catalytic performance of assembled ceria necklace nanowires by Ni doping

Ceria and nickel-doped ceria necklace-like nanowires were synthesized by a facile, surfactant free method, through an unconventional assembly route. Homogeneous doping of lower-valent cations introduces elastic strain, resulting in extrinsic surface defects and higher catalytic performance in CO oxidization.