Activation of Open‐Cage Fullerenes with Ruthenium Carbonyl Clusters

Reactions of the open‐cage fullerene C₆₃NO₂(Py)(Ph)₂ ( 1 ) with [Ru₃(CO)₁₂] produce [Ru₃(CO)₈(μ,η⁵‐C₆₃NO₂(Py)(Ph)₂)] ( 2 ), [Ru₂H(CO)₃(μ,η⁷‐C₆₃N(Py)(Ph)(C₆H₄))] ( 3 ), and [Ru(CO)(Py)₂₍η³‐C₆₃NO₂(Py)(Ph)₂)] ( 4 ), in which the orifice sizes are modified from 12 to 8, 11, and 15‐membered ring, through ruthenium‐mediated C?O and C?C bond activation and formation.     

A theoretical investigation of low energy band gap polymers: polythiophene systems

Recently, the organic synthesis and electronic device applications of π-conjugated polymer-based materials with low energy band gap (below 2 eV) and high values of incident photon to current efficiency have been presented. In the present study, the physical properties of polythiophene (PTH) and its derivative systems (PTs) were investigated as π-conjugated low energy band gap polymers. Density functional theory with periodic boundary condition (PBC), the B3LYP functional, and the 6-31G(d) basis set was applied to determine their geometric and electronic structures and corresponding energies (E _HOMO, E _LUMO, and E _g = E _LUMO ? E _HOMO) from the monomer of thiophene and its derivatives for one-dimensional (1D) extension to polymer. The effects of 3-substitution in PTs including electron-donating (CH₃–, C₆H₁₃–, OH–, Cl–, OCH₃–, and CHO–) and electron-withdrawing groups (Cl–, CHO–, CN–, NO₂–, CF₃–, and COOH–) compared with PTH were investigated. According to the calculation results, PTs with electron-donating and electron-withdrawing substituents should exhibit red- and blue-shifts, respectively, compared with PTH. These calculation results show good agreement with experimental data and provide further information for molecular design considerations.     

Well-posedness of the Hydrodynamic Model for Semiconductors

This paper concerns the well-posedness of the hydrodynamic model for semiconductor devices, a quasi-linear elliptic–parbolic–hyperbolic system. Boundary conditions for elliptic and parabolic equations are Dirichlet conditions while boundary conditions for the hyperbolic equations are assumed to be well-posed in L² sense. Maximally strictly dissipative boundary conditions for the hyperbolic equations satisfy the assumption of well-posedness in L² sense. The well-posedness of the model under the boundary conditions is demonstrated.     

Alcohol Selective Optical Sensor Based on Porous Cholesteric Liquid Crystal Polymer Networks

A responsive hydrogen-bonded cholesteric liquid crystal polymer (CLCP) film with controlled porosity was fabricated as an optical sensor to distinguish between methanol and ethanol in alcohol solutions. To facilitate responding the alcohols, porosity was generated by removing the nonreactive liquid crystal agent, and the hydrogen bridges of CLCP were broken. The sensitivities of CLCPs to ethanol and methanol were obtained by monitoring the wavelength shifts of the transmission spectrum at different alcohol concentrations and ratios of methanol/ethanol. Changes in the central wavelength of the CLCP network transmission spectrum allowed the methanol–ethanol ratio to be discriminated. A linear relationship between wavelength shift of CLCP networks and alcohol concentration was obtained experimentally, and the sensor characteristics were explored. The sensitivities of the CLCPs were 1.35 and 0.18 nm/% to ethanol and methanol, respectively. The sensing sensitivity of cholesteric networks to alcohol molecules increased as the methanol–ethanol ratio declined. Therefore, CLCP could act as a stimuli-responsive material to distinguish the concentrations of acetone and ethanol in mixed solutions. Furthermore, the impact of UV intensity for curing a CLC mixture on the sensing sensitivity to the different alcohol concentrations was also studied. The higher UV intensity could enhance the sensitivity to alcohol molecules and distinguishing ability between methanol and ethanol.     

Carbon Encapsulation of High Entropy Alloy Nanoparticles with Extraordinary Coercivity and Saturation at Room Temperature

Owing to their unique properties and technological potential, high entropy alloys (HEAs) have become the subject of great interest in the materials science community. HEAs consist of more than four principle elements in equimolar ratio so their configurational entropy is intrinsically greater than one-principle element based. The increasing surface energy and chemical tendency toward clustering of like atoms at low dimension, however, make production of HEA-nanoparticles (HEA-NPs) extremely difficult. A facile production of HEA-NPs inside carbon nanotubes and nanoparticles is demonstrated in this work. Electron microscopic and elemental analyses confirm encapsulated to be solution phase; some embrace carbides and form multidomains with chemical composition ranging from quaternary to quinary phase. Multidomains and nonmagnetic centers create hardening thus promoting coercivity significantly at room temperature. Alloying induces electron redistribution into high spin states, accounting for observed high saturation. Configurational entropy of encapsulated HEA-NPs lies on a range comparable with bulk.     

Analyses of preservatives by capillary electrochromatography using methacrylate ester-based monolithic columns

Five common food preservatives were analyzed by capillary electrochromatography, utilizing a methacrylate ester-based monolithic capillary as separation column. In order to optimize the separation of these preservatives, the effects of the pore size of the polymeric stationary phase, the pH and composition of the mobile phase on separation were examined. For all analytes, it was found that an increase in pore size caused a reduction in retention time. However, separation performances were greatly improved in monolithic columns with smaller pore sizes. The pH of the mobile phase had little influence on separation resolution, but a dramatic effect on the amount of sample that was needed to be electrokinetically injected into the monolithic column. In addition, the retention behaviors of these analytes were strongly influenced by the level of acetonitrile in the mobile phase. An optimal separation of the five preservatives was obtained within 7.0 min with a pH 3.0 mobile phase composed of phosphate buffer and acetonitrile 35:65 v/v. Finally, preservatives in real commercial products, including cold syrup, lotion, wine, and soy sauces, were successfully determined by the methacrylate ester-based polymeric monolithic column under this optimized condition.     

Preparation and properties of amino-terminated anionic waterborne-polyurethane-silica hybrid materials through a sol-gel process in the absence of an external catalyst

A series of polymer-silica hybrid materials consisting of amino-terminated anionic waterborne-polyurethane (WPU) and inorganic silica particles have been prepared through a sol-gel process in the absence of an external catalyst. Typically, amino-terminated anionic WPU was first synthesized from polycaprolactone, dimethylol propionic acid, and 4,4′-methylenebis(cyclohexyl isocyanate) with specific molar ratios, followed by further reaction with triethylamine and triethylene tetramine to give as-prepared WPU. The WPU obtained was characterized by FTIR spectroscopy and gel permeation chromatography. Subsequently, a series of hybrid materials with different silica contents were prepared by performing sol-gel reactions with tetraethyl orthosilicate (TEOS) in an amino-terminated WPU matrix without the addition of an external catalyst. This was followed by examination by transmission electron microscopy and ²⁹Si solid-state NMR. The terminated primary amine groups attached to the as-prepared WPU chains functioned as an internal base catalyst for the sol-gel process of TEOS. The effect of composition on the thermal stability, mechanical strength, surface wettability, and optical clarity of the hybrid materials was evaluated by the thermogravimetric analysis, dynamic mechanical analysis, contact angle measurement, and UV-visible transmission spectroscopy, respectively.     

Effect of annealing cold-drawn polystyrene and polymethylmethacrylate below Tg

Annealing of both cold-drawn atactic polystyrene and cold-drawn poly-methylmethacrylate at temperatures ranging from 50°C to their respective T_g's and for times ranging from 1 to 6 days gradually but completely eliminates the orientation arcing from the wide-angle X-ray diffraction pattern but induces only ～25% recovery of the cold-drawn deformation (as calculated from dimensional shrinkage). Analogous studies show that the birefringence of cold-drawn polystyrene is reduced by 57% during the annealing treatment. The results are evidence for segmental molecular motion below T_g and suggest that the molecular alignment responsible for the wide-angle X-ray diffraction arcing is not necessarily the same molecular orientation required for dimensional recovery. We have tentatively interpreted these results in terms of our recently proposed structural model consisting of both ordered domains and connecting disordered regions in the amorphous polymeric solid state. Annealing below T_g can produce chain backbone motion within the disordered regions and cause disorientation of the aligned ordered domains brought about by the initial cold-draw process.