Materials Literature
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In spite of considerable effort, the understanding of the molecular structure of polyacry-lonitrile-based fibers is still incomplete. This paper shows that molecular modeling based on molecular mechanics and dynamics can be used to study the molecular structure of polyacrylonitrile-based fibers with appropriate strate…
Multiblock copolymers offer the possibility to combine the properties of different polymers. Thus, new materials with tailor-made unique properties are available by coupling of different suitable polymeric segments. The goal of the work discussed in this paper was to combine advantageous properties of liquid-crystalli…
Freshwater ecosystems are a major component of the northern environment. The application of new limnological technologies and approaches to these ecosystems is producing a revised perspective on their structure and dynamics, and is leading to insights into their potential response to global change processes. The plank…
The first comprehensive survey on the uses of alkyl polyglycosides as renewable ressources for the chemical industry. Experts from industry show in detail how alkyl polyglycosides can help chemists to improve their products. Since quite a few years, renewable Ressources are of increasing interest for the chemical indu…
The improvement of flame-retardation of thermosetted epoxy–amine resins was attempted by chemically incorporating phosphorus-containing reagents. By reacting 4,4′-diglycidylether of bisphenol A (DGEBA) with dialkyl (or aryl) phosphate, it was possible to chemically modify the epoxy resin and then cure it in the presen…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectral Dynamics of Individual Molecules in Glasses and CrystalsE. Geva, P. D. Reilly, and J. L. SkinnerView Author Information Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706Cite this: Acc. Chem. Res. 1996, 29,…
We reconsider a number of measurements for the overall hydration kinetics of tricalcium silicate pastes having an initial water to cement weight ratio close to 0.5. We find that the time dependent ratio of hydrated and unhydrated silica mole numbers can be well characterized by two power-laws in time, $x/(1-x)\sim (t/…
The strain induced by lattice mismatch at the interface is responsible for the different value of the band discontinuities observed recently for the AlN/GaN (AlN on GaN) and the GaN/AlN (GaN on AlN) polar (0001) interface. We present a first-principles calculation of valence band offsets, interface dipoles, strain-ind…
There exists a generic relationship between the thermodynamics of a continuous polymer with a generic self-interaction and the two-point function of an interacting field-theory. In addition, the (2N)-point function of the resulting field theory is similarly related to a system of N interacting polymers. In the present…
A continuum model derived from an atomistic Hamiltonian is used to examine the ordering kinetics in CuAu. A detailed description of the formation of the low and high temperature ordered and modulated superlattice states is given. The metastability of the modulated phase at low temperatures is shown to severely hinder…
I consider the effects of polymers on the smectic phase of a host liquid-crystal matrix. Focusing on the regime in which the polymers are predominatly confined between the smectic layers, I find that the presence of the polymers can lead to a re-entrant phase diagram with the smectic-C sandwiching the smectic-A phase…
A novel intramolecular allylic migration from silicon to carbon was observed during the reaction of allylmethyldichlorosilane with tropolone in the presence of triethylamine to give an isomeric mixture of pentacoordinate silicon compounds having allylated tropolonato ligand. The molecular structure of the major isomer…
An oblate rhombohedral unit cell of α-boron crystal was constructed and the transition of two icosahedra lying at the ends of its short body diagonal was simulated. By applying ab initio Hartree-Fock self-consistent field methods different configurations of two icosahedra were investigated. The obtained structure B 24…
Quasicrystals are solids with quasiperiodic atomic structures and symmetries forbidden to ordinary periodic crystals-e.g., 5-fold symmetry axes. A powerful model for understanding their structure and properties has been the two-dimensional Penrose tiling. Recently discovered properties of Penrose tilings suggest a sim…
New ferrocenyl dendritic macromolecules based on flexible poly(propylenimine) dendrimer cores, built up to the fifth generation, containing 4, 8, 16, 32, and 64 peripheral ferrocenyl moieties, have been prepared and characterized. Solution electrochemical studies showed that all the ferrocenyl redox centers attached t…
To demonstrate that crystallographic methods can be applied to index and interpret diffraction patterns from well-ordered quasicrystals that display non-crystallographic 5-fold symmetry, we have characterized the properties of a series of periodic two-dimensional lattices built from pentagons, called Fibonacci pentili…
We study the approach to global breakdown in disordered media driven by increasing external forces. We first analyze the problem by mean-field theory, showing that the failure process can be described as a first-order phase transition, similarly to the case of thermally activated fracture in homogeneous media. Then we…
We study the behavior of fracture in disordered systems close to the breakdown point. We simulate numerically both scalar (resistor network) and vectorial (spring network) models with threshold disorder, driven at constant current and stress rate respectively. We analyze the scaling of the susceptibility and the clust…
It has been recently observed that synthetic materials subjected to an external elastic stress give rise to scaling phenomena in the acoustic emission signal. Motivated by this experimental finding we develop a mesoscopic model in order to clarify the nature of this phenomenon. We model the synthetic material by an ar…
We present an exact calculation to show that an infinite Sierpinski gasket fractal supports an infinite number of extended electron states. We work within the real space renormalization group (RSRG) scheme and show that by analysing the recursion relations for the Hamiltonian parameters one can extract the eigenvalues…