Materials Literature
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Abstract The possibility of phase transformation toughening is demonstrated by the example of the β‐modification of isotactic polypropylene (β‐iPP), which undergoes βα‐transformation (i.e., from hexagonal to monoclinic) during mechanical loading. The resulting α‐iPP exhibits a higher crystalline density than the initi…
A titanium-containing mesoporous material with a cubic structure, Ti-MCM-48, is synthesized by a two-stage hydrolysis method using tetraethylorthosilicate and tetrabutylorthotitanate and found to be more active than Ti-MCM-41 in the epoxidation of bulky alkenes using H2O2.
We have determined the phase behavior of a series of model poly(ethylene)−poly(ethylethylene) (PE−PEE) diblock copolymers with poly(ethylene) block volume fractions ( f PE ) ranging from 0.25 to 0.46. Four ordered microstructures make contact with the ODT: spheres arranged on a body-centered cubic lattice ( Im 3̄ m sp…
Poly(acrylic acid), poly(vinylsulfonate) and poly(styrenesulfonate) have been incorporated between the positively charged sheets of layered double hydroxides (LDHs)M1–xAlx(OH)2+(M = Mg, Ca, Co) and Zn1–xM′x(OH)2+(M′= Al, Cr) to form layered nanocomposites. The resulting nanocomposites contained the LDH sheet structure…
The adsorption and reaction properties of Rh particles supported on a CeO 2 (100) surface and on polycrystalline CeO 2 films annealed at low (LT, 970 K) and high (HT, 1720 K) temperatures were studied using temperature-programmed desorption (TPD) and steady-state, CO oxidation kinetics. SEM and XRD of the polycrystall…
We report data on using the emulsion-based method for the assembly of ball-like aggregates of a positively charged (amidine) latex. The latex particles are strongly hydrophobized with the use of sodium dodecyl sulfate, which induces their adsorption into the bulk of the emulsion droplets. The droplets are then sterica…
Stable palladium particles were found to be readily prepared from aqueous solutions of palladium(II) chloride by ultrasonic irradiation (200 kHz, 6.0 W/cm2) in the presence of protective agents (RH). The average sizes of particles were 6 and 7.5 nm from solutions of 0.1 and 0.5 mM of Pd(II)-containing poly(vinylpyrrol…
The complex formation of bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF) with 29 organic electron acceptors and six organic anions yielded 37 charge-transfer (CT) complexes, about three-quarters of which exhibited metallic behavior. The BEDO-TTF molecule proves to be an excellent source for stable metals irrespective…
Most of the diffraction data for silica, the prototypical network glass, can be understood through local structural parameters. Failures to fit the prominent first (sharp) diffraction peak (FSDP), giving vital clues to medium-range order, are spectacular, however. We show a correspondence between FSDPs in glasses and…
Ti-, V-, Cr-, Mo-, and Mn-substituted hexagonal mesoporous silicas prepared at ambient temperature by electrostatic (S+ X–I+) and neutral (S0 I0) surfactant templating pathways are catalytically active for the peroxide hydroxylation of benzene to phenol in the absence of a solvent.
The deuterated tris(hexafluoroacetylacetonato)neodymium(III) complex, Nd(HFA-D) 3, was obtained by keto−enol tautomerism reaction of Nd(HFA) 3 in methanol- d 4 . The emission of Nd(HFA-D) 3 was observed in the following anhydrous deuterated organic solvents: methanol- d 4, acetone- d 6, THF- d 8, DMF- d 7, and DMSO- d…
The adsorption of flexible polymers from dilute solution in good solvents at attractive walls is studied by Monte Carlo simulation of a coarse-grained off-lattice model, varying chain length N and the strength ε of a short-range attractive wall potential. Unlike many previous studies, no chain end (or other monomer) i…
A series of mesoporous vanadosilicate VMCM-41 molecular sieves with variable Si/V ratios have been hydrothermally synthesized at pH 11 using 2-propanol as a phase stabilizer. The chemical environment of the vanadium centers in VMCM-41 is investigated by powder X-ray diffraction (XRD), electron probe microanalysis (EPM…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTDiblock Copolymer NanofibersGuojun Liu, Lijie Qiao, and Andrew GuoView Author Information Department of Chemistry, The University of Calgary, 2500 University Drive, NW, Calgary, Alberta, Canada T2N 1N4Cite this: Macromolecules 1996,…
We characterize the phase behavior of a series of polystyrene−poly(2-vinylpyridine) diblock copolymers ( M w ∼ 20 000 g/mol) using dynamic mechanical spectroscopy, transmission electron microscopy, small-angle neutron scattering, and small-angle X-ray scattering. Measurements on symmetric diblocks ( f PS = 0.5) permit…
A new universal inelastic mean free pathlength (IMFP)-predictive equation (the G1 equation) has been formulated for use in the analytical electron spectroscopies XPS and AES which essentially states that the IMFP of an electron traversing matter is inversely proportional to the atomic density. The equation is based on…
The first examples of organic polymer-layered silicic acid nanocomposites have been prepared by formation of a cured epoxy polymer network in the presence of organo cation-exchange forms of magadite. The transparency of the exfoliated magadiite hybrid is an especially notable property.
The type and concentration of hydroxy groups in MCM-41 as a function of the Si:Al ratio have been investigated and compared with amorphous Si/Al oxide. Three hydroxy groups at 3745, 3715 and 3530 cm–1 were observed in the IR spectra of siliceous MCM-41. For Al-containing samples the intensity of the bands at 3715 and…
Template-assembled collagen-based polypeptides KTA-[Gly-(Gly-Pro-Hyp) n -NH 2 ] 3 ( n = 1, 3, 5, 6; KTA is cis, cis -1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid, also known as the Kemp triacid) and acetyl-terminated single-chain collagen-based analogs Ac-(Gly-Pro-Hyp) n -NH 2 ( n = 1, 3, 5, 6, 9) were synthesi…
The crystal structure of holo D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from the extreme thermophile Thermus aquaticus has been solved at 2.5 Angstroms resolution. To study the determinants of thermostability, we compare our structure to four other GAPDHs. Salt links, hydrogen bonds, buried surface area, pack…