Materials Literature
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The order−disorder transition (ODT) and the ordering kinetics have been studied in four-arm star diblock copolymer melts of styrene (corona) and isoprene (core) by rheology and SAXS. The results are compared with the corresponding linear diblock and show that the transition shifts in the direction predicted by theory.…
A viscoplastic model is presented for distributing the deformation applied to a polycrystal in a non-uniform fashion among the constituent crystals. Interactions with surrounding crystals are incorporated in the calculation of the deformation rate of each crystal through an appropriately defined local neighborhood. A…
A peroxo titanic acid (PTA) solution has been prepared by mixing titanic acid wet gel and hydrogen peroxide solution. The PTA solution was a neutral, transparent, stable liquid. The PTA crystallized to form an anatase phase after calcination at a temperature above 250°C. When the PTA solution was autoclaved at a tempe…
The fluorescence properties of two macrocyclic ligands incorporating bis-(β-naphthyl amide) groups, –CH2CON(CH2C10H7)2, as fluorophores, have been studied in water and acetonitrile. The ligands exhibit distinctive luminescence behaviour in the presence of quenching (e.g. Pb2+, Ni2+, Cu2+ and Eu3+) and non-quenching io…
The surface composition of electrically conductive polypyrrole-coated polystyrene latex particles has been examined by X-ray photoelectron spectroscopy (XPS). We have systematically characterized the surface of polystyrene (PS), poly( N -vinylpyrrolidone) (PNVP), chloride-doped polypyrrole (PPyCl) powder, and PNVP-sta…
New deposits of saponite have been described recently in the Madrid Basin (Madrid and Toledo provinces, Central Spain), a zone very rich in Mg silicates, especially in sepiolite. This is the first time that the high surface area saponitic material from Yunclillos deposit (Toledo province) is described. The acid treatm…
{HB(Butpz)3}Mg(OEt) in CH2Cl2 at 22 °C acts as a catalyst precursor for the fast, stereoselective, ring-opening polymerization of L,L-dilactide by the acyl cleavage mechanism yielding isotactic poly(L,L-dilactide) with PDI ≈ 1.2.
A cubic BC2.5N solid solution (c-BC2.5N) was synthesized in 18% yield by shock-compression of a hexagonal BC2.5N compound. c-BC2.5N was confirmed to have a diamond structure without a long range order of atomic arrangement. The material is a polycrystal composed of microcrystals of 5–20 nm in size. All constituent ato…
Tetrakisarylporphyrins are conveniently chlorosulphonated in high yields.These chlorosulphonyl compounds may he converted in high yield into sulphonic acid derivatives through reaction with a variety of nucleophiles so as to give, for example, the free sulphonic acid, a sulphonamide or a sulphonate ester.
The silylation of borosilicate with APTS ((γ-aminopropyl)triethoxysilane) is studied as a tool to improve zeolite incorporation in PI (polyimide) films. Among other experimental parameters, a quantification of the zeolite outer surface silanols is performed in order to determine the most appropriate silylation conditi…
High-resolution electron microscopy (HREM), combined with digital image processing and computer simulation techniques, has been used to carry out a microstructural characterization of some Rh/TiO2 catalysts reduced at 473, 773 or 823 K. A sample resulting from the reduction of the catalyst at 773 K, reoxidized with fl…
Silica pillared Ca 2 Nb 3 O 10 was prepared from the layered perovskite KCa 2 Nb 3 O 10 via alkylammonium ion intercalated Ca 2 Nb 3 O 10 . The obtained materials were characterized by XRD, TEM, NMR, and BET measurements. The interlayer spacing increased in parallel with the length of the alkyl chain of intercalated a…
The driving force behind the research on advanced materials has largely been aerospace and defense applications. In such applications the customer-induced limitations and infrastructural economic factors are secondary to the application-oriented parameters. Automobiles, on the other hand, represent the primary consume…
The incorporation of divalent cations (Mg2+, Mn2+, Cu2+, Sr2+, Cd2+, Ba2+ and Pb2+) in vaterite and calcite has been studied by atomic absorption spectroscopy (AAS), optical and scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) spectroscopy. The samples of vaterite a…
Adsorption of HCl, HBr, NO and SO 3 on nanoscale MgO (autoclave prepared = AP-MgO) and microscale MgO (conventionally prepared = CP-MgO) has been studied. The higher surface area of AP-MgO allows a higher capacity of these gases to be adsorbed/mol MgO. However, at pressures of 100 Torr or higher, the amounts adsorbed/…
Abstract Construction of dendritic macromolecules based on the mimicry of macroscopic branching patterns found in trees is reviewed. From this mimicry, synthetic strategies have been developed for the preparation of precise macromolecular building blocks referred to as Starburstr̀/Cascade dendrimers. These dendrimer c…
High-impact-modified polystyrene (HIPS) is made by thermal or radical polymerization of styrene containing dissolved polybutadiene (PB). The reaction leads, intermediately, to blends of yet ungrafted PB, of the homopolymer PS, and of graft copolymers PBgS varying in the number of PS grafts per PB chain. The polymeriza…
This paper presents a general overview of calcification and involves aspects of the chemical, physical, and biological nature of mineral crystals in invertebrate and vertebrate tissues, with selected examples of the latter. Two broad areas are described: mineral structure and composition. Mineral formation is detailed…
Eight tris(organotin)-substituted Keggin tungstosilicate heteropolyanions have been synthesized and characterized by elemental analysis, infrared and Mössbauer spectroscopy, multinuclear NMR, and X-ray crystallography. The new anions contain alpha- or beta-SiW(9)O(34)(10)(-) moieties and are of two structural types, […
Transient absorption measurements with subpicosecond resolution have been performed on nickel(II) dodecaphenylporphyrin (NiDPP), a highly nonplanar tetrapyrrole. Following photoexcitation, NiDPP deactivates by the pathway (π,π*) → (d,d) → ground state, the route proposed previously for planar analogues. However, the (…