Materials Literature
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During spherulitic crystallization of polymers, there is a tendency for low molecular weight and other less crystallizable entities to be rejected from the body of the spherulites. This rejection process causes a segregation of these species to those areas where spherulites impinge. As a result of this segregation, la…
Transport properties of polyaniline (PANI)--cellulose acetate (CA) conducting blends have been investigated at various length scales and temperatures. We report on the results of dc and ac conductivity measurements, magnetoresistance and electron-spin resonance (ESR) performed on composite films with PANI weight fract…
The influence of ion bombardment on the nucleation and growth of diamond films by microwave plasma chemical vapor deposition (CVD) has been investigated. The following findings were obtained. (i) Modification of surface diffusion by a substrate bias voltage was demonstrated by the measurement of the first-nearest-neig…
The first part of a series of two, this paper analyzes the degradation of pure and filled PTFE under high energy UV radiation. The polymer morphology is first investigated using differential scanning calorimetry, highlighting the respective nucleating efficiency of TiO2 and CaF2 during polymer crystallization. Then, t…
Polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the films obtained has been investigated. It was found that the thickness of the film and ambient relative humidity (RH) were crucial to the motion of film: An increase of the film thickness decreased the…
Two new triphenylamine-based bis (o-aminophenol) monomers, 4,4′-diamino-3,3′-dihydroxytriphenylamines, were successfully synthesized by the cesium fluoride-mediated condensation of 2-(benzyloxy)-4-fluoronitrobenzene with aniline derivatives, followed by simultaneous deprotection and reduction. Aromatic polybenzoxazole…
Segmented polyetherurethane (SPEU) materials based on polytetramethylene oxide (PTMO, Mw 1000 and 2000) with various hard-segment contents were synthesized and their biocompatibilities studied via different tests. The static contact angle data reveal that the higher hard-segment-content SPEU material possesses a lower…
The isotropic–nematic phase transition in a fluid of hard spherocylinders with a spherocylindrical square-well attraction is examined using Monte Carlo simulations and two theoretical approaches. The first theory is a first-order perturbation theory which incorporates the Parsons decoupling approximation for the pair…
A new aromatic tetracarboxylic dianhydride having a crank and twisted noncoplannar structure, 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, was synthesized by the reaction of 4-nitrophthalonitrile with biphenyl-2,2′-diol, followed by hydrolysis and cyclodehydration. The biphenyl-2,2′-diyl-containing aromatic pol…
We investigate the molecular mechanism of secondary nucleation on a growth surface of the polymer crystal. We adopt a simplified model of polyethylene molecule made of 500 beads connected by springs, and consider the crystallization from a vapor phase neglecting surrounding molecules. A strongly collapsed chain in a v…
A miscibility phase diagram of mixtures of UV-curable multifunctional thiolene-based optical adhesive (NOA65) and low molar mass 4- n -heptyl-4-cyanobiphenyl nematic liquid crystal (K21) has been established using light scattering, optical microscopy, and differential scanning calorimetry. The emergence of phase morph…
Surface relaxations and electronic structures of (001) surfaces of cubic ${\mathrm{SrTiO}}_{3}$ have been studied by first-principles total-energy calculations with the generalized-gradient approximation. Both ${\mathrm{TiO}}_{2}$-terminated (surface-I) and SrO-terminated (surface-II) surfaces are investigated and the…
Magneto-optical Kerr effects have been investigated for perovskite-type hole-doped oxides ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3} (0<~x<~0.3)$ and ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3} (0<~x<~0.3)$ in the photon energy range between 0.9 and 5.3 eV…
We use tight-binding total-energy calculations to investigate the energetics and the cap formation mechanism of single-walled carbon nanotubes. The present calculations of the edge energy and strain energy suggest the growth of armchair nanotubes to be energetically more favorable than the growth of zigzag nanotubes.…
The yield stress behavior of a range of polyethylene materials which differ with respect to their short chain branch content has been studied. Measurements carried out over a wide range of temperatures have shown that there is a sudden transition in the behavior of the yield stress at a temperature which is dependent…
Au/SrTiO 3 (STO), Au/YBa2Cu3O7−x (YBCO)/STO, Au/STO/CeO2/STO, and Au/STO/MgO/STO multilayer structures on LaAlO3 substrates have been fabricated. Their properties are investigated at 1 MHz and at microwave frequencies (40 MHz–40 GHz) as a function of applied voltage, and in the temperature range between 20 and 300 K.…
A structural analysis of six alkaline sodium aluminate aqueous solutions by the X-ray diffraction method is reported. On average, each Al atom is surrounded by four oxygens, indicative of the predominance of Al(OH) 4 - (aq) in these solutions. Detailed least-squares fitting indicates that a significant contraction of…
The voltage-dependent dielectric constant (ε) of SrTiO3 (STO) thin films is the basis for developing cryogenic capacitors for tunable microwave applications. In this study, the effect of microwave signal level on nonlinear response at 1.7–1.9 GHz was examined by measuring the level of the third order intermodulation d…
We have studied the influence of the anodization temperature on the formation of porous Si for different current intensities. We have monitored the porosity, growth rate, luminescence, refractive index, and porous Si/bulk Si interface roughness. A strong decrease of the roughness was obtained for low temperature anodi…
Ferroelectric thin films (∼1.2 μm) of BaxSr1−xTiO3 with gradients in composition normal to the growth surface were formed on platinum substrates by metalorganic decomposition. Effective (pseudo) pyroelectric coefficients as large as 0.06 μC/cm2 K have been obtained from these active ferroelectric devices under the app…