Materials Literature
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A growing group of polyfunctional precursors of polymer networks contains more than one branch point (cross-link). The bonds they extend lead either to another branch point or to a functional group. When such precursors are cross-linked, these branch points are gradually activated to reach the status of elastically ac…
Thiol-derivatized gold clusters (i.e. nano-sized gold crystals coated with a thiolate monolayer, Aun(SR)m, with m ≪ n) based on n-alkanethiols have been obtained by treatment of gold clusters embedded in poly(N-vinylpyrrolidone) (PVP) with thiols. Dodecanethiol (DDT), hexadecanethiol (HDT), and octadecanethiol (ODT) h…
Novel two-dimensional octupoles containing azo groups and their oligomers have been synthesized and their first hyperpolarizabilities were determined. The λmax and β(0) values of azo octupoles are nearly the same regardless of the nature of the bridge or the conjugation length. On the other hand, 1,3,5-tricyano-2,4,6-…
A combination of characterization techniques has been employed to obtain a full description of the structure and chemical state of a series of Co−W/SiO 2 catalysts used for the production of single-walled carbon nanotubes (SWNT) by CO disproportionation at 750−950 °C. The state of Co and W on a series of silica-suppor…
We report the results of experiments to estimate the moisture expansion of several modern and ancient clay brick ceramics from the time of manufacture. From these data we propose a new expansion law, in which the expansive strain increases as (age)(1/4) approximately. Such time dependence is consistent with a mechanis…
Using ab initio local spin-density-functional formalism, we study the occurrence of spin polarization in quasi-one-dimensional heterostructured C/BN nanotubes. At the zigzag boundary connecting carbon and boron nitride segments of tubes, we find atomiclike states that acquire magnetization when partly filled. Whereas…
Abstract Blends of two semicrystalline polymers, poly( L ‐lactic acid) (PLLA) and poly‐ p ‐dioxanone (PPD) have been prepared by solvent casting in different compositions. Thermal, morphological, and mechanical properties of the blends were studied using modulated differential scanning calorimetry, wide‐angle X‐ray di…
Density functional theory has been used to study the effects of solvent coordination on the structure and formation of the titanium hydroperoxo species believed to be the active intermediate in oxidation reactions with Ti(IV)−H 2 O 2 catalytic systems. Titanium hydroperoxo intermediates possessing a variety of coordin…
Enzymelike kinetics were observed in the hydrolysis of 7-hydroxy-1-methylquinolium esters 2 under the catalysis of three of a family of synthetic peptide dendrimers 1. Their synthesis was based on a symmetrical branching diamino acid (B), three variable amino acid positions (A1, A2, A3=His, Asp, Ser), and a disulfide…
The calculated structures of a supported Rh6 cluster (depicted) demonstrate that protons of surface OH groups of the oxide support migrate onto the cluster. This migration results in the oxidation of metal atoms that are in close contact with the support. The energy released by this reverse hydrogen spillover is estim…
For the first time, the molecular weight distribution and extent of side reactions have been quantified in polyurethane prepolymers. A combination of NMR, size exclusion chromatography, and mass spectrometry has been used to measure the molecular weight distribution. The values obtained are consistent with Flory's ste…
Be my guest: A new family of supramolecular inclusion compounds is introduced which relies upon second-sphere hydrogen-bonding interactions to assemble highly stable layered networks (see picture). These solids have great potential for structural variation. They are possibly inorganic analogues of a well-studied host…
Morphology evolution, anisotropic phase behavior, and orientational behaviors of the highly filled polymer-organically modified layered silicate nanocomposites are investigated by using synchrotron small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and polarized light microscopy (PLM). Two kin…
Following a bottom-up approach to nanomaterials, we present a rational synthetic route to high-spin and anisotropic molecules based on hexacyanometalate [M(CN)(6)](3-) cores. Part 1 of this series was devoted to isotropic heptanuclear clusters; herein, we discuss the nuclearity and the structural anisotropy of nickel(…
Following a bottom-up approach to nanomaterials, we present a rational synthetic route from hexacyanometalates [M(CN)(6)](3-) (M=Cr(III), Co(III)) cores to well-defined heptanuclear complexes. By changing the nature of the metallic cations and using a localised orbital model it is possible to control and to tune the g…
Silica chemistry in the living world. Some microorganisms, such as diatoms (see figure), have learned to build up finely patterned mineral structures by using the many possibilities of silica chemistry and adapting themselves to its constraints. Association of biomimetic chemical approaches with molecular biology tech…
Pairs of atomic scale terraces on a single crystal metal surface can be made to merge controllably under suitable conditions to yield steps of double height and width. We study the effect of various physical parameters on the formation of defects in a kinetic model of step doubling. We treat this manifestly non- equil…
A solid-on-solid model is proposed to describe faceting of bcc(111) metal surface induced by a metal overlayer. It is shown that the first order phase transition occurs between faceted {211} or {110} and disordered phases. The ordered phases consist of large 3-sided pyramids with {211} facets or {110} facets. It is sh…
For fermions with degenerate single-particle energy levels, the usual relation between the total number of particles and the chemical potential $μ$ is only satisfied for a specific number of particles, i.e. those leading to closed shells. The treatment of an arbitrary number of fermions requires a modification of the…
We study the relation of the potential energy landscape (PEL) topography to relaxation dynamics of a small model glass former of Lennard-Jones type. The mechanism under investigation is the hopping between superstructures of PEL minima, called metabasins (MBs). Guided by the idea that the mean durations <tau> of visit…