Materials Literature
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The effects of polymerization temperature and the amount of chain extender, 2,2‘-bis(2-oxazoline), on the synthesis of lactic acid based poly(ester−amide) (PEA) were studied. High molecular weight polymer was produced only within a narrow range of polymerization parameters. The highest molecular weights were achieved…
Nanoscale palladium and nickel colloids prepared in the presence of certain tetra- n -octylammonium carboxylates contain a high proportion of nonequilibrium trigonal cross section particles. Specifically, those carboxylates which bear a hydroxy function at the α -position, e.g., tetra- n -octylammonium glycolate, exer…
The melt-state linear viscoelastic properties for a series of intercalated nanocomposites are examined. The nanocomposites are based on a short disordered polystyrene−polyisoprene diblock copolymer and varying amounts of dimethyldioctadecylammonium modified montmorillonite. The linear dynamic oscillatory moduli and th…
A simple process has been developed to create large area, highly uniform microporous thin films. Multilayers of weak polyelectrolytes were assembled onto silicon substrates by the sequential adsorption of poly(acrylic acid) and poly(allylamine) from aqueous solution. These multilayers were then immersed briefly into a…
A detailed multifrequency high-field-high-frequency EPR (95-285 GHz) study has been performed on the single-molecule magnet of formula [Fe8O2(OH)12(tacn)6]Br8⋅9 H2O, in which tacn=1,4,7-triazacyclononane. Polycrystalline powder spectra have allowed the estimation of the zero-field splitting parameters up to fourth ord…
We have studied the exchange-correlation hole and pair correlation function in the valence shell of the ground-state of the Si atom, using accurate Slater-Jastrow wavefunctions and the Variational Monte Carlo method. The exchange-correlation hole shows a number of interesting features caused by the open shell structur…
7Li NMR measurements were performed in the metallic spinel LiV2O4. The temperature dependencies of the line width, the Knight shift and the spin-lattice relaxation rate were investigated in the temperature range 30 mK < T < 280 K. For temperatures T < 1 K we observe a spin-lattice relaxation rate which slows down expo…
We investigate numerically a simple microscopic model to describe wearless dry friction between atomically flat contact interfaces without thermal fluctuations (T=0K). The analysis of the incommensurate ground state shows a breaking of analyticity when the amplitude $ε$ of the Lennard-Jones interaction between the bot…
Nanoscale architecture was used to control energy transfer in semiconducting polymers embedded in the channels of oriented, hexagonal nanoporous silica. Polarized femtosecond spectroscopies show that excitations migrate unidirectionally from aggregated, randomly oriented polymer segments outside the pores to isolated,…
Stress, strain, and optical birefringence were measured for a series of peroxide-cured natural rubbers, having both isotropic and double network structures. The residual stretch (permanent set) for the latter ranged from 2.0 to 4.5, with elastic moduli that were an increasing function of this residual strain, as found…
S4(AsF6)2.AsF3 was prepared by the reaction of sulfur with arsenic pentafluroide in liquid AsF3 (quantitatively) and in anhydrous HF in the presence of trace amounts of bromine. A single-crystal X-ray structure of the compound has been determined: monoclinic, space group P2(1)/c, Z = 4, a = 7.886(1) A, b = 9.261(2) A,…
A new kind of inorganic self-assembled monolayer (SAM) was prepared by spontaneous adsorption of polyoxometalate anion, AsMo 11 VO 40 4 -, onto a gold surface from acidic aqueous solution. The adsorption process, structure, and electrochemical properties of the AsMo 11 VO 40 4 - SAM were investigated by quartz crystal…
Four dendrimers (1b-4b) containing chiral vicinal diol-based subunits were prepared from their acetonide-protected precursors (1a-4a). The optical activity of these chiral dendritic structures was successfully modeled using structurally similar, low molecular weight model compounds. Using the [Phi](d) values of the lo…
Three new polynuclear copper(II) complexes, derived from the end-on azido bridging ligand and pyridine derivatives, have been synthesized, and their crystal structures have been determined by X-ray diffraction methods; they are the dinuclear compounds [Cu2(mu 1,1-N3)2(4-Etpy)4(mu-NO3)2] (1), and [Cu2(mu 1,1-N3)2(3-amp…
Centrin and calmodulin (CaM) are closely related four-EF-hand Ca(2+)-binding proteins. While CaM is monomeric, centrin 2 is dimeric and binds only two Ca(2+) per dimer, likely to site IV in each monomer. Ca(2+) binding to centrin 2 displays pronounced negative cooperativity and a [Ca(2+)](0.5) of 30 microM. As in CaM,…
The first conducting polythiophene, having only dendritic solubilizers, has been prepared using a Stille coupling approach. The use of second and third generation aliphatic ether convergent dendrons as a solubilizing platform facilitated the preparation of dendrimer-oligothiophene hybrid macromonomers having minimal s…
Chlorins provide the basis for plant photosynthesis, but synthetic model systems have generally employed porphyrins as surrogates due to the unavailability of suitable chlorin building blocks. We have adapted a route pioneered by Battersby to gain access to chlorins that bear two meso substituents, a geminal dimethyl…
The effect of magnesium and zinc on the growth kinetics of a hydroxyapatite (0001) face in pseudophysiological solutions was investigated. The growth rates of the (0001) face were measured under various concentrations of magnesium or zinc using Moire phase shift interferometry coupled with surface observation by atomi…
We investigate the effective conductivity ($σ_e$) of a class of amorphous media defined by the level-cut of a Gaussian random field. The three point solid-solid correlation function is derived and utilised in the evaluation of the Beran-Milton bounds. Simulations are used to calculate $σ_e$ for a variety of fields and…
We investigate the influence of fractal structure on material properties. We calculate the statistical correlation functions of fractal media defined by level-cut Gaussian random fields. This allows the modeling of both surface fractal and mass fractal materials. Variational bounds on the conductivity, diffusivity and…