Materials Literature
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A heuristic treatment of the connectedness Ornstein–Zernike equation is developed for macromolecular fluids within the framework of the polymer reference interaction site model (PRISM). Results are presented for the critical volume fraction at the percolation threshold and for the mean number of interchain contacts pe…
The mechanism of the enzymatic degradation of poly([R]-3-hydroxybutyrate) (PHB) was investigated by using well-defined model substrates, including both linear and cyclic [R]-3-hydroxybutyrate (3HB) and [R]-3-hydroxyvalerate (3HV) oligomers, with two different PHB depolymerases. The linear and cyclic oligomers containi…
Three different lithium manganese(III) oxides (the orthorhombic LiMnO 2 phase, monoclinic layered LiMnO 2 and tetragonal Li 2 Mn 2 O 4 ) were studied with 6 Li magic-angle spinning (MAS) NMR spectroscopy. Much smaller shifts of 36−143 ppm are observed for the Mn(III) phases, in comparison to the other lithium manganes…
We show that the emeraldine base form of polyaniline (PANI) forms self-organized (mesomorphic) structures upon mixing with an amphiphilic oligomer zinc dodecyl benzenesulfonate, Zn(DBS) 2 . The number of Zn(DBS) 2 molecules vs the number of PhN repeat units of PANI was selected to be x = 0, 0.125, 0.25, 0.5, and 1.0,…
The oxidation state of Cu species dispersed in a Cu-ZSM-5 zeolite obtained by a nonconventional gas-phase CuCl exchange, and nominally containing only Cu(I) species, was studied by x-ray photoelectron spectroscopy (XPS) and x-ray absorption near edge structure (XANES) analyses. The oxidation of Cu(I) species to Cu(II)…
An alternating deposition film of a copolymer of p -(hexaflouro-2-hydroxylisopropyl)-α-methylstyrene and styrene (PSOH) and poly(4-vinylpyridine) (PVP) was fabricated on the basis of hydrogen bonding between hydroxyl and a pyridine ring in chloroform. It is found that the selection of solvent is very important for suc…
A simple theoretically motivated model to extrapolate the correlation energy based on correlation-consistent polarized X-tuple basis sets is suggested. It has the form EXcor=E∞cor[1+A3 X−3(1+A4 X−1)], where EXcor is the energy for the X-tuple basis set, E∞cor and A3 are parameters to be determined from a set (Xmin−Xma…
Electrostatic layer-by-layer thin films may be directed to specific regions of a surface based on electrostatics, secondary interactions, and steric repulsion. In this study, a series of polyamines ranging from hydrophobic polyallylammonium hydrochloride (PAH) to hydrophilic linear polyethyleneimine (LPEI) were coadso…
Viscosity measurements in a broad temperature range display a variation over 11 orders of magnitude and show a crossover at about T+=285 K, comparable with dielectric results from a Stickel evaluation. The index R, i.e., the product of dielectric loss peak maximum frequencies times the viscosity, divided by temperatur…
Periodic mesoporous organosilicas with two-dimensional and three-dimensional hexagonal as well as cubic ( Pm 3 n ) symmetry were synthesized using bridged silsesquioxane species (RO) 3 Si−CH 2 −CH 2 −Si(RO) 3 as precursors and cetyl- or octadecyltrimethylammonium chloride (C 16 TMACl or C 18 TMACl) as structure-direct…
Transmetalation of polylithiated, carbosilane (CS) dendrimers functionalized with the potentially terdentate ligand [C 6 H 2 (CH 2 NMe 2 ) 2 -2,6-R-4] - ( = NCN) with NiCl 2 (PEt 3 ) 2 produced a series of nickel-containing dendrimers [G0]-Ni 4 ( 4 ), [G1]-Ni 12 ( 5 ), and [G2]-Ni 36 ( 7 ) in moderate to good yields.…
The effect of the inclusion of As antisites in the diluted magnetic semiconductor (Ga,Mn)As is studied within density functional theory in the local spin density approximation. In the case of homogeneous distribution of Mn ions we find that the ferromagnetism is largely weakened by the presence of the antisites. This…
NiFe 2 O 4 nanocrystals were dispersed in silica by a sol−gel route. The dried gel was amorphous, in which isolated Fe 3+ ions had a weak interaction with silica matrix, as characterized by a weak IR absorption at ca. 580 cm -1 . Heat treatment at 400 °C resulted in nickel ferrite clusters being partially formed, and…
Experiments on surface melting of several organic materials have shown contradictory results. We study the Van der Waals interactions between interfaces in surface melting of the bulk CH_4 and interfacial melting of the CH_4 film on the MgO substrate. This analysis is based on the theory of Dzyaloshinskii, Lifshitz, a…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTUnusual pH-Dependent Polarity Changes in PAMAM Dendrimers: Evidence for pH-Responsive Conformational ChangesWei Chen, Donald A. Tomalia, and James L. ThomasView Author Information Department of Chemical Engineering and Applied Chemi…
A novel and direct method is described for conjugating protein molecules to luminescent CdSe−ZnS core−shell nanocrystals (Quantum Dots) for use as bioactive fluorescent probes in sensing, imaging, immunoassay, and other diagnostics applications. The approach makes use of a chimeric fusion protein designed to electrost…
The chemical oxidative polymerization of diphenylamine-4-sulfonate (DPASA) was carried out in aqueous and 0.5 M H 2 SO 4 solutions using potassium peroxodisulfate (PDS) as an oxidant. The course of polymerization was followed by UV−visible spectroscopy. The absorbances corresponding to the intermediate and the polymer…
Using the methods of atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, chemical etching of the (010) surface of flux-grown orthorhombic MoO 3 (α-MoO 3 ) single crystals has been investigated in detail. The (010) surface was etched repeatedly in a 0.08 M NaOH aqueous solution, and…
A [2]-rotaxane Zn 2 −Au + made from a dumbbell component ended by Zn(II) porphyrin stoppers and a ring component incorporating a Au(III) porphyrin has been assembled in 13% yield using the transition metal templating route. 1 H NMR studies show that its conformation in solution is very different from those of its comp…
The soliton model for motion of the 90° partial in silicon has provided an explanation for the large reduction in activation energy (1 eV) which occurs under prolonged exposure to an H plasma. Applying the same theoretical model to diamond yields a drop of 1.6 eV and puts dislocation motion into the realm of the possi…