Materials Literature
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Hyperbranched aromatic polycarbonates were prepared by the polymerization of an A 2 B monomer derived from 1,1,1-tris(4‘-hydroxyphenyl)ethane. Protection of one of the three phenols of the triphenol by a tert -butyldimethylsilyl group was followed by conversion of the remaining two phenolic groups to carbonylimidazoli…
A photothermal microscope that provides micrometer lateral and submicrometer depth resolution was designed. Thermal conductivity measurements with modulation frequencies up to 12 MHz on single grains in polycrystalline diamond demonstrate its lateral resolution power even for a highly conducting material. Measured con…
The electro-optical behavior of polymer stabilized cholesteric texture cells has been investigated for three different polymers. The switching process was studied with respect to the electric field dependence of the diffuse reflectivity, diffuse transmittance, and the dynamics of the reorientation process. For certain…
Abstract A new model for the interpretation of dioctahedral mica infrared (IR) spectra in the OH stretching vibration region is proposed. It is based on the analysis of the main factors responsible for the observed sequence of the OH frequencies. In terms of this model, the simple analytical dependence between the OH…
Dynamic mechanical spectroscopy (DMS) is used to further investigate the recently observed order−disorder transition (ODT) in comblike block copolymers obtained by hydrogen bonding between poly(4-vinylpyridine) and pentadecylphenol (P4VP−PDP x ). For stoichiometric amounts of pyridine and phenol, i.e., x = 1.0, the OD…
Mechanical behavior of the Space Shuttle redesigned solid rocket motor (RSRM) propellant is studied from a phenomenological point of view. Motivated by the study of the experimental data three initially isotropic constitutive models have been developed. All models represent the effect of strain rate, superimposed hydr…
We present a review of some results concerning electronic transport properties of quasicrystals. After a short introduction to the basic concepts of quasiperiodicity, we consider the experimental transport properties of electrical conductivity with particular focus on the effect of temperature, magnetic field, and def…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSolid-Supported Hyperbranched Polymerization: Evidence for Self-Limited GrowthP. Bharathi and Jeffrey S. MooreView Author Information Roger Adams Laboratory, Departments of Chemistry and Materials Science & Engineering The Beckman Institute for Advanced Science and Tec…
A model is proposed to describe all experimental results on electrical aging of cables reported in Part 1. It is based on simple thermodynamics concepts in the Eyring theory, includes the concept of submicrocavity formation proposed by Zhurkov, and supposes that the first step in electrical aging is essentially a mole…
The photo-oxidative stability of various annelated and substituted tetraazaporphyrin derivatives were investigated in N , N -dimethylformamide by irradiation in the presence of air. First-order rate constants were calculated. In addition, the positions of the HOMO and LUMO energy levels of the compounds were calculate…
The evaporation of silicon carbide (SiC) ceramics during sintering has been studied by thermogravimetry in a graphite furnace filled with argon. The SiC powder compacts contained 7.5 wt% eutectic composition of Y 2 O 3 –Al 2 O 3 to promote liquid‐phase sintering. A weight loss of 1–11 wt% was observed during sintering…
Polycrystalline boron nitride (BN) films are synthesized using BCl 3 and N 2 as source gases, by plasma-assisted chemical vapor deposition. BN films consist of nanocrystalline grains of 3 nm in size. The energy gap is estimated to be 6.0 eV from ultraviolet-visible optical transmission measurement. The electrical resi…
Shape memory alloys (SMAs) have several unique characteristics, including their Young's modulus-temperature relations, shape memory effects, and damping characteristics. The Young's modulus of the high-temperature austenite of SMAs is about three to four times as large as that of low-temperature martensite. Therefore,…
Unidirectional elongation of magnetic field sensitive polymer gels, called ferrogels, have been studied. In ferrogels, finely distributed colloidal particles having superparamagnetic behavior are incorporated into a swollen network. These particles couple the shape of the gel to the nonuniform magnetic field. Shape di…
In its physiological solid state, type I collagen serves as a host for many types of cells. Only the molecules on fiber surface are available for interaction. In this interfacial environment, the conformation of a cell binding domain can be expected to fluctuate between the collagen fold and a distinctive non-collagen…
{5-[[[2‘,5‘-Bis[(4‘‘-( n -(perfluoroalkyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]bicyclo[2.2.1]hept-2-ene}s were polymerized by ring-opening metathesis polymerization in THF at 40 °C using Mo(CHCMe 2 Ph)(N-2,6- i Pr 2 Ph)(O t Bu) 2 as the initiator. 2,5-Bis[(4‘-( n -(perfluoroalkyl)alkoxy)benzoyl)oxy]toluenes mimic bo…
A method to fabricate one dimensional nanoscale composite based on coating of carbon nanotube with metal is proposed and demonstrated in this letter. Carbon nanotubes have been coated with a layer of nickel by electroless plating. It was found that the nickel coating had a tendency to form as nanoparticles on the surf…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPolyphosphazene Block Copolymers via the Controlled Cationic, Ambient Temperature Polymerization of PhosphoraniminesHarry R. Allcock, Scott D. Reeves, James M. Nelson, Chester A. Crane, and Ian MannersView Author Information Departm…
A new series of nonlinear optical molecules are described where the ground state polarization is predominantly zwitterionic when the molecules are dissolved in solution. The molecules, which are derived in general from facile reactions between tertiary amines and tetracyano- p -quinodimethane (TCNQ), are of a type whe…
Refractive indices and extinction coefficients have been calculated for 14 oxide and fluoride thin films over a wavelength range of 0.6-12 mum. Results from adhesion, abrasion, and humidity testing have been included to characterize the durability of each film. The data allow selection of the best oxide and fluoride m…