Synthesis of an amphiphilic spiro-multiblock copolymer via thiol-ene click chemistry

A multiblock [poly(ethylene oxide)-b-spiro-polystyrene] ([(PEO-b-spiro-PS)]) copolymer with a topologically novel architecture was synthesized using thiol-ene step-growth polymerization reaction. Spiro-PS with dimercapto groups as the hard segment was synthesized in three main steps: (a) preparation of tetra-arm PS by atom transfer radical polymerization and the conversion of the chain-end group to azide functionality, (b) alkyne-azide click coupling reaction to synthesize a tricyclic PS, and (c) tactical ring opening of the tricyclic PS through disulfide/thiol redox reaction. The PEO soft segment was obtained as chain-ends modified with norbornene groups. Finally, the hydrothiolation of the highly reactive norbornene chain-ends of polyethylene glycol with the dimercapto groups of spiro-PS produced the multiblock ([(PEO-b-spiro-PS)]) copolymer in quantitative yield. The multiblock copolymer was characterized using size-exclusion chromatography, proton nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 132–138     

A new design strategy for dispersion stabilization of Ni particles based on the surface acid and base properties of Ni particles

A dispersion technology for Ni particles suspended in a non-aqueous medium based on the quantitative evaluation of surface acid-base properties of Ni particles is described. A quantitative analysis of surface acid-base properties of Ni particles was performed using non-aqueous titration. Dimethylamino ethanol and acetic acid were used as probe molecules to detect surface acid-base amounts of Ni particles. The dispersion system was designed on the basis of the amounts of surface acid-base sites on the Ni particle surface. Rheological behavior and agglomerate particle size data demonstrate that the dispersion stability of the designed Ni suspension is markedly improved, as expected. Therefore, the design strategy to improve the dispersion stability of Ni particles was successful. This strategy is expected to be applicable to dispersion systems of other particles suspended in a non-aqueous medium.     

Copper–Organic Framework Fabricated with CuS Nanoparticles: Synthesis,Electrical Conductivity,and Electrocatalytic Activities for Oxygen Reduction Reaction

To apply electrically nonconductive metal–organic frameworks (MOFs) in an electrocatalytic oxygen reduction reaction (ORR), we have developed a new method for fabricating various amounts of CuS nanoparticles (nano‐CuS) in/on a 3D Cu–MOF, [Cu₃(BTC)₂?(H₂O)₃] (BTC=1,3,5‐benzenetricarboxylate). As the amount of nano‐CuS increases in the composite, the electrical conductivity increases exponentially by up to circa 10⁹‐fold, while porosity decreases, compared with that of the pristine Cu‐MOF. The composites, nano‐CuS(x wt %)@Cu‐BTC, exhibit significantly higher electrocatalytic ORR activities than Cu‐BTC or nano‐CuS in an alkaline solution. The onset potential, electron transfer number, and kinetic current density increase when the electrical conductivity of the material increases but decrease when the material has a poor porosity, which shows that the two factors should be finely tuned by the amount of nano‐CuS for ORR application. Of these materials, CuS(28 wt %)@Cu‐BTC exhibits the best activity, showing the onset potential of 0.91 V vs. RHE, quasi‐four‐electron transfer pathway, and a kinetic current density of 11.3 mA cm^?2 at 0.55 V vs. RHE.     

Multifunctionality and crystal dynamics of a highly stable, porous metal-organic framework [Zn4O(NTB)2

A porous metal-organic framework [Zn(4)O(NTB)(2)].3DEF.EtOH (1), in which (3,6)-connected nets are doubly interpenetrated to generate curved three-dimensional channels, has been prepared. Framework 1 exhibits high permanent porosity (Langmuir surface area, 1121 m(2)/g; pore volume, 0.51 cm(3)/cm(3)), high thermal stability (up to 430 degrees C), high hydrogen adsorption capacity (1.9 wt % at 77 K and 1 atm), selective organic guest binding ability (K(f)()( )(): MeOH > pyridine > benzene > dodecane), and guest-dependent blue luminescence (lambda(max) depending on guest identity). Most interestingly, the framework sustains single crystallinity even at 400 degrees C and 10(-)(5) Torr, and the framework components undergo reversible dynamics, mainly rotational motion, in response to removal and rebinding of the guest molecules.     

Investigating sorption on iron-oxyhydroxide soil minerals by solid-state NMR spectroscopy: a 6Li MAS NMR study of adsorption and absorption on goethite

High-resolution 2H MAS NMR spectra can be obtained for nanocrystalline particles of goethite (alpha-FeOOH, particle size approximately 4-10 nm) at room temperature, facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, the system representing an ideal model system for NMR studies. 6Li resonances with large hyperfine shifts (approximately 145 ppm) were observed above the goethite point of zero charge, providing clear evidence for the presence of Li-O-Fe connectivities, and thus the formation of an inner sphere Li+ complex on the goethite surface. Even larger Li hyperfine shifts (289 ppm) were observed for Li+-exchanged goethite, which contains lithium ions in the tunnels of the goethite structure, confirming the Li assignment of the 145 ppm Li resonance to the surface sites.     

Power-Law Behavior in Geometric Characteristics of Full Binary Trees

Natural river networks exhibit regular scaling laws in their topological organization. Here, we investigate whether these scaling laws are unique characteristics of river networks or can be applicable to general binary tree networks. We generate numerous binary trees, ranging from purely ordered trees to completely random trees. For each generated binary tree, we analyze whether the tree exhibits any scaling property found in river networks, i.e., the power-laws in the size distribution, the length distribution, the distance-load relationship, and the power spectrum of width function. We found that partially random trees generated on the basis of two distinct types of deterministic trees, i.e., deterministic critical and supercritical trees, show contrasting characteristics. Partially random trees generated on the basis of deterministic critical trees exhibit all power-law characteristics investigated in this study with their fitted exponents close to the values observed in natural river networks over a wide range of random-degree. On the other hand, partially random trees generated on the basis of deterministic supercritical trees rarely follow scaling laws of river networks.     

Effects of satellite positioning errors and Earth’s multipole moments in the detection of the gravitomagnetic field with an orbiting gravity gradiometer

The paper deals with a dynamical system analysis related to phantom cosmological model. Here gravity is coupled to phantom scalar field having scalar coupling function and a potential. The field equations are reduced to an autonomous dynamical system by a suitable redefinition of the basic variables and assuming some suitable form of the potential function. Finally, critical points are evaluated, their nature have been analyzed and corresponding cosmological scenario has been discussed.     

Detection of the gravitomagnetic field using an orbiting superconducting gravity gradiometer: principle and experimental considerations

The angular momentum of the Earth produces gravitomagnetic components of the Riemann curvature tensor, which are of the order of 10⁻¹⁰ of the Newtonian terms arising from the mass of the Earth. Due to the dragging of the local inertial frame by the spinning Earth, there are also secular terms, which grow in time. These fields can be detected in principle by a set of orbiting superconducting gravity gradiometers. The Riemann tensor components for various spacecraft orientations have been computed and the principle of detecting the gravitomagnetic tidal force has been published. In this paper, we review the conclusions of the earlier analyses and discuss the feasibility of the gravity gradiometer experiment.