Materials Literature
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The response times and operating voltages for light shutters made from polymer dispersed liquid crystals' are studied. Alterations in the resistivity of the polymer binder are made by varying the degree of cross-linking to demonstrate and quantitize the strong effect of resistivity on the switching voltage. The v…
We discuss the conditions under which the electric fields produced by polarization space charge need to be included in calculating the response of ferroelectric liquid crystals to applied electric fields. We present a simple example to illustrate the basic physical effect of polarization space charge and apply the res…
Diffusion of a metal (Cu) into a fully cured polymer (polyimide) below the glass transition has been systematically investigated for the first time by means of low-energy ion sputtering in combination with a radiotracer technique. The penetration profiles exhibit a steep non-Fickian decay of the tracer concentration o…
An equivalent weight series of short-side-chain perfluorosulfonic polymers has been studied in the sulfonyl fluoride, sulfonic acid, and sodium sulfonate forms by dynamic mechanical spectroscopy, differential scanning calorimetry, and wide angle X-ray scattering. Results indicate that the functional form of the polyme…
The crystallization of the minor component in incompatible polymer blends starts sometimes at distinctly larger undercoolings than in the pure polymer, and proceeds in several separated steps. After a short survey on the history of the effect in the available literature, the several types and the origin of this "fract…
This chapter provides a broad overview of the subjects of polymer blends and ionomers. Specific topics concerning polymer blends include the thermodynamics of mixing of polymer-polymer pairs, polymer interfaces, rheology, and mechanical properties. For ionomers, the chemistry, structure, rheology and solution properti…
This chapter provides a broad overview of the subjects of polymer blends and ionomers. Specific topics concerning polymer blends include the thermodynamics of mixing of polymer-polymer pairs, polymer interfaces, rheology, and mechanical properties. For ionomers, the chemistry, structure, rheology and solution properti…
Abstract Water sorption and diffusion has been measured in polyamide–imide over a range of temperature and relative humidities. The results are compared to those obtained on Kapton and discussed in terms of chemical differences between these two materials. Changes in dielectric loss during hydrothermal aging under 85°…
Abstract Samples of crosslinked cis ‐polybutadiene were crystallized at different temperature and drawing degree. The melting behavior of the crystallized samples was analyzed detecting the retractive stress as a function of temperature. The experimental melting data were extrapolated to the equilibrium conditions to…
Abstract The reaction between diisocyanates and diepoxides can produce polyoxazolidones. However, the reaction may be accompanied by concurrent cyclization of isocyanate to produce trimeric isocyanurate. Studies were performed with pure phenyl isocyanate or diphenylmethane‐4,4′‐diisocyanate (MDI) and the diglycidyl et…
Abstract Micro- and macroscopic aspects of large-strain deformation are examined through analyses of shear by using physical and phenomenological models. Past experiments and analyses are first reviewed to reveal current issues and put the present work in perspective. These issues are addressed by a complete set of si…
Abstract The high temperature engineering thermoplastic poly(aryl‐ether–ether‐ketone) (PEEK) has been subjected to dynamic and isothermal thermogravimetry in both nitrogen and air. The dynamic data have been analyzed using both the Kissinger peak maximum technique and an isoconversional procedure developed by Flynn. T…
Abstract The reaction of molten HDPE with MAH at 215 and 250°C using di‐ t ‐amyl peroxide and t ‐butyl cumyl peroxide as catalysts yielded HDPE‐ g ‐MAH accompanied by crosslinked polymer. The formation of the latter, increased by the presence of MAH and insoluble in refluxing xylene, was prevented by the presence of e…
The planar defects which are commonly observed in deposited Co-Cr and Co-Ni-Cr magnetic thin films have been characterized by electron microdiffraction and trace analysis. It was unambiguously shown that these planar defects are (0001) stacking faults, which are thought to be formed to reduce the growth stress of the…
The equilibrium quasicrystal phase of a two-dimensional two-component Lennard-Jones atomic system and two different ensembles of random tilings (binary and uncontrained) are analyzed by means of Monte Carlo simulations. We find that the quasicrystal phase in the atomic system is well described by the random-tiling mod…
We investigate the quasicrystalline state of a two-dimensional binary alloy in a discrete tiling approximation. Through transfer-matrix calculations we determine the configurational entropy over a range of concentrations. We find that the entropy density is maximized by a state with tenfold symmetry at the quasicrysta…
Experimentally it is well known that diamond and zinc-blende semiconductors show an ``unusual'' (i.e., negative) thermal expansion at about 100 K. We performed density-functional-theory calculations of thermodynamic potentials (i.e., total energies and entropies) for perfect crystals, to study the temperature dependen…
Mg 2+ . C 6 H 8 O 8 2- .2H 2 O cristallise dans Cc avec a=7,605, b=8,785 et c=16,404 A, β=92,56˚, Z=8; affinement jusqu'a R=0,052. L'ion galactarate est centrosymetrique et l'ion Mg 2+ a une coordination six (octaedrique). Les distances Mg-O varient de 2,003 a 2,117A
Cristallisation dans Pmnn avec a=5,861, b=20,200 et c=4,501 A, Z=2; affinement jusqu'a R=0,054. U 6+ et Ni 2+ sont localises en feuillets perpendiculaires a [OOz] et entoures d'octaedres. Les atomes B sont en groupes BO 3 triangulaires ou BO 4 tetraedriques et stabilisent la cohesion dans les trois directions. Les oct…
With numerical calculations it is shown that in a Fibonacci superlattice, in a magnetic field parallel to the layers, the self-similarity in the length scale is reproduced in the energy-level structure. In particular, the cyclotron-orbit-center dispersion of the energy levels shows a field-dependent structure which is…