Materials Literature
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We compare the swelling of surface-attached neutral poly(4-vinylpyridine) (PVP) and charged poly( N -methyl-4-vinylpyridinium iodide) (MePVP) brushes under good solvent conditions using multiple-angle null ellipsometry. The polymer layers were prepared by the “grafting from” technique, where a low molecular mass initi…
We report electron paramagnetic resonance measurements on single crystalline and powder samples of ${\mathrm{Nd}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ across the charge-ordering transition at ${T}_{\mathrm{co}}=240\mathrm{K}$ down to the antiferromagnetic ordering transition at ${T}_{N}=140\mathrm{K}.$ The chan…
We have developed a route for the synthesis of 2'-selenium uridine analogues and oligonucleotides containing selenium labels, and have demonstrated for the first time a new strategy to covalently derivatize nucleotides with selenium for phase and structure determination in X-ray crystallography.
A large scale synthesis of carbon nanofibers with a controlled diameter of about 50 nm has been achieved at relatively low temperatures (550–650 °C) by the decomposition of ethane on a carbon nanotube supported nickel catalyst. The carbon nanofibers can be used as a catalyst or a catalyst support without subsequent pu…
Recently, polymer–clay hybrid materials have received considerable attention from both a fundamental research and application point of view.1–3 This organic–inorganic hybrid, which contains a nanoscale dispersion of the layered silicates, is a material with greatly improved physical and mechanical characteristics. The…
Photocyclization and photocycloreversion quantum yields of three diarylethene derivatives were determined in the single-crystalline phase. The former yields in the crystalline phase were twice as large as those in solution. This can be attributed to only photoreactive antiparallel conformers being packed in the crysta…
Using state of the art time-dependent density functional theory and multireference second-order perturbation theory, we have accurately calculated (within 0.3 eV) in real space the optical gap of small silicon quantum dots, with diameters up to 25 A. Our results, which support the quantum confinement hypothesis, are i…
Mixed perovskites (AA‘)(BB‘)O 3, where A = La or Nd, A‘ = Sr, B = Al or Ga, and B‘ = Ta or Nb, were investigated by X-ray photoelectron spectroscopy (XPS). The interpretation of XPS O(1s) signals in mixed oxides is discussed. The nonsingular O(1s) peak that occurs in the mixed oxides is due to the polarization of the…
We present a new and general mechanism for inter-conversion of carbon structures via a catalytic exchange process, which operates under conditions of Frenkel pair generation. The mechanism typically lowers reaction barriers by a factor of four compared to equivilent uncatalysed reactions. We examine the relevance of t…
We describe a method for creating atomic-scale electric contacts. A metal source is deposited on two insulating substrates separated by a 70 nm gap. Electric conductance across the gap is monitored, while protrusions from the bulk extend into the gap and reach corresponding protrusions on the other side of the gap. Wh…
The variational approach to weakly nonlocal thermodynamic theories is critically revisited in the light of modern nonequilibrium thermodynamics. The example of Ginzburg-Landau equation is investigated in detail.
The spontaneous polarization and the piezoelectric constants of ZnO and BeO are calculated at an ab initio quantum-mechanical level by using two alternative strategies, namely, through the Berry phase scheme applied to delocalized crystalline orbitals, and through the definition of well-localized Wannier functions. Th…
Abstract Poly(3‐hydroxybutyrate) (PHB)/poly(glycidyl methacrylate) (PGMA) blends were prepared by a solution‐precipitation procedure. The compatibility and thermal decomposition behavior of the PHB/PGMA blends was studied with differential scanning calorimetry, thermogravimetric analysis, and differential thermal anal…
Abstract Supertough nylon 11 is prepared by using a plasticizer. The influence of plasticizers on the impact property and tensile properties of plasticized nylon 11 were investigated. The results show that the impact strength is improved remarkably by methylbenzene sulfonamide, and the tensile strength is almost the s…
Abstract A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω‐alkanediols with oxadiazole‐activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5‐bis(4‐fluorophenyl)‐1,3,4‐oxadiazole and various…
Abstract A series of new thermotropic main‐chain liquid crystalline copolyesters were prepared by polycondensation of 2,6‐naphthalenedicarbonyl chloride, 4,4′‐thiodiphenol, and α,ω‐alkanediols ( n = 4–10) in diphenyl ether at 200°C. Thermal transition behaviors of these copolyesters were investigated by differential s…
The graft copolymerization of methyl methacrylate onto mercaptochitin and some properties of the resulting graft copolymers have been studied. Methyl methacrylate was efficiently graft copolymerized onto mercaptochitin in dimethyl sulfoxide, and the grafting percentage reached 1300% under appropriate conditions. Altho…
Methacrylate derivatives bearing β-D-glucopyranoside and β-D-galactopyranoside residues are synthesised by glycosylation of 2-hydroxyethyl methacrylate (HEMA) with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide and 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide, respectively. β-Selectivity in the glycosylation…
Reduction of an excess of arsenic with a solution of sodium in liquid ammonia yields the thermally unstable title compound [Na(NH3)5]2As(4).3NH3, which contains isolated square-planar As4(2-) ions with a mean As-As bond length of 2,345 A.
Coordination to a Zn(II) center of chelating π-delocalized nitrogen donor ligands such as 5-X-1,10-phenanthrolines (X = OMe, NMe 2, trans- CH CHC 6 H 4 - 4‘ - NMe 2, trans,trans -(CH CH) 2 C 6 H 4 - 4‘ - NMe 2 ) produces a significant enhancement of their quadratic hyperpolarizability measured either by the EFISH tech…