Materials Literature
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Abstract End‐group modified hyperbranched polyetherimides were prepared by a one‐pot, two‐step reaction sequence. General synthetic techniques were developed to prepare both monofunctional terminating segments and the corresponding modified polyetherimide hyperbranched polymers. Monofunctional groups were used to term…
In the Gram-positive bacterium Bacillus subtilis the concentration of the amino acid L-arginine is controlled by the transcriptional regulator AhrC. The hexameric AhrC protein binds in an L-arginine-dependent manner to pseudo-palindromic operators within the promoter regions of arginine biosynthetic and catabolic gene…
We develop a theory to describe the reorientation phenomena in the lamellar phase of block copolymer melts under reciprocating shear flow. We show that, similar to the steady shear, the oscillating flow anisotropically suppresses fluctuations and gives rise to the [parallel]--> [perpendicular] transition. The experime…
Langmuir−Blodgett (LB) films of dilithium octacyanophthalocyanine [Li 2 Pc(CN) 8 ] were first prepared, and their electrochemical reduction/reoxidation behaviors were studied in detail. An overwhelming majority of the Li 2 Pc(CN) 8 molecules in the LB film were stacked in a face-to-face aggregated state and stood obli…
A solvent-free method for preparing electrically conductive polyurethane foams and elastomeric films is described. The method consists of impregnation of the oxidant into the foam through the sublimation of iodine, followed by in situ polymerization of pyrrole using pyrrole vapors to obtain a polypyrrole/polyurethane…
Surface functionalization of low-density polyethylene (LDPE), silanized glass, and free-standing polyaniline (PANI) films via UV-induced graft copolymerization with 1,1‘-bis(4-vinyl-benzyl)-4,4‘-bipyridinium dichloride (VBV) was carried out. The vinyl group containing viologen was synthesized by the double Anderson re…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTStructural Investigation of Ag−Pd Clusters Synthesized with the Radiolysis MethodCarmen M. Doudna, Massimo F. Bertino, and Akira T. TokuhiroView Author Information Department of Physics, University of MissouriRolla, Rolla, Missouri 65409, and Department of Nuclear Engineering,…
An initial photophysical study of a tetra-solketal-substituted zinc phthalocyanine is reported; at low temperature this compound exhibits very strong aggregation, and a new red shifted emission peak is observed, lambda max approximately 750 nm, attributed to a fluorescent phthalocyanine dimer.
The electronic conductivity of the Dion−Jacobson-type layered perovskite NaCa 2 Nb 3 O 10 was determined by employing ac impedance measurements using ion-blocking electrodes, electron-blocking electrodes, and dc Hebb−Wagner polarization measurements using NaCoO 2 as the reversible reference electrode. Oxygen partial-p…
The determination of the three-dimensional structures of biological macromolecules by X-ray diffraction generally requires large good-quality crystals, which are often difficult to obtain as crystal nucleation and growth depend upon a great number of physicochemical parameters. In the future, the emergence of structur…
Carbonaceous mesophases are discotic nematic liquid crystals that are spun into high performance carbon fibers using the melt spinning process. The spinning process produces a wide range of different fiber textures. Planar polar (PP) and planar radial (PR) textures are two ubiquitous ones. This paper presents theory a…
Layered Ni,Zn hydroxyacetates have been prepared by hydrothermal methods and have been used for anion exchange of the original acetate anions by chloride, bromide, carbonate, nitrate, sulfate, and phosphate. Exchange was complete in all cases. The solids have been characterised by elemental chemical analysis, powder X…
Nanoparticles of improved stability against long-term aggregation were prepared using poly(styrene)- b -poly(2-vinylpyridine) (PS- b -P2VP) star-block copolymer architectures. The star-block copolymers, physically resembling diblock copolymer micelles, were synthesized by anionic polymerization and coupling with ethyl…
Several water-soluble cobalt(III) complexes were employed as precursors to form cobalt oxide nanostructures. These complexes were incorporated into polyelectrolyte multilayers precoated onto colloidal particles, followed by calcination. Cobalt complexes with strong intermolecular hydrogen bonding form one-dimensional…
Abstract The effects of ultraviolet (UV) radiation and thermal annealing on the optical and mechanical properties of polyvinyl alcohol (PVA) were studied. Pure PVA samples were prepared by casting technique. Xenon arc lamp was used to irradiate the sample. The irradiated PVA sample was heated at 150°C for 2 h. The opt…
Carbon single-wall nanotubes (SWNTs) grow efficiently from methane on alumina-supported metal catalysts within a fairly narrow temperature window from 680 to 850 °C. An abrupt onset in SWNT growth occurs at the low temperature side of the window, and SWNTs produced at these lower temperatures appear to be relatively f…
We use steady-shear rheology to study the shear-disordering phenomenon in block copolymers in the body-centered-cubic (bcc) mesophase. Polystyrene−polyisoprene and polystyrene−poly(ethylene- alt -propylene) diblock, triblock, and starblock systems of varying molecular weight and composition were studied in the melt an…
Most studies of self-assembled systems reveal that the highest order is associated with equilibrium states of the system. By systematically studying metal decoration of diblock copolymer templates, I show that a high degree of order can arise under strongly nonequilibrium conditions. Under a wide range of conditions,…
Flash-cooling and annealing of macromolecular crystals have been investigated using in situ X-ray imaging, diffraction-peak lineshape measurements and conventional crystallographic diffraction. The dominant mechanisms by which flash-cooling creates disorder are suggested and a fixed-temperature annealing protocol for…
Amorphous tungsten oxide has been prepared by ultrasound irradiation of a solution of tungsten hexacarbonyl W(CO)6 in diphenylmethane (DPhM) in the presence of an Ar (80%)–O2 (20%) gaseous mixture at 90 °C. Heating this amorphous powder at 550 °C under Ar yields snowflake-like dendritic particles consisting of a mixtu…