Materials Literature
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The structure and crystallization kinetics of poly(ethylene oxide) (PEO) in the homopolymer and in two triblock copolymers of poly(ethylene oxide)−polystyrene−poly(ethylene oxide) (PEO−PS−PEO), crystallized from the ordered melt, have been studied respectively with X-ray diffraction, optical microscopy and differentia…
Recent observations of the disorder−order transition for colloidal hard spheres under microgravity revealed dendritic crystallites roughly 1−2 mm in size for samples in the coexistence region of the phase diagram. Order of magnitude estimates rationalize the absence of large or dendritic crystals under normal gravity…
The iron(II) spin-crossover compound [Fe(ptz)(6)](PF(6))(2) (ptz = 1-propyltetrazole) crystallizes in the triclinic space group P&onemacr;, with a = 10.6439(4) Å, b = 10.8685(4) Å, c = 11.7014(4) Å, alpha = 75.644(1) degrees, beta = 71.671(1) degrees, gamma = 60.815(1) degrees, and Z = 1. In [Fe(ptz)(6)](PF(6))(2), th…
The power loss of MnZn ferrites and its relation to average grain size and grain boundary properties was investigated. The power loss was found to be dependent on the average grain size and on the highly electrically resistive grain boundaries which are formed by introduction of aliovalent ions in the outer grain regi…
Using the technique of fluorescence piezospectroscopy, we determine the distribution of thermal residual stresses across the edges of three laminated alumina/zirconia composites. We develop a methodology for separating the measured stress state into microstresses that result from grain‐to‐grain thermal mismatch and ma…
The disappearance of ferroelectricity in Pb(Zr0.52,Ti0.48)O3 (PZT) thin-film capacitors, which is caused by heat treatment in a reductive ambience, is investigated. Bare PZT films are not damaged by annealing in a hydrogen-containing atmosphere (H2 annealing) up to 400 °C, whereas a PZT capacitor with Pt electrodes lo…
The diffracted orders generated by a plane-wave incident upon a multilayered dielectric grating can undergo strong intensity variations known as Wood’s anomalies or scattering resonances. To clarify these effects, we examine the field and power flux inside the grating region by using a rigorous modal solution of the s…
The reactivity toward dioxygen of two series of dicobalt cofacial diporphyrins in solution in an aprotic solvent is described. Some of these compounds are efficient electrocatalysts for the four-electron reduction of dioxygen when adsorbed on a graphite electrode immersed in aqueous acid. Their electrochemical and spe…
Reaction of beta-functionalized alcohols of type HOCR(2)CH(2)do (1a, do = OMe, R = Me; 1b, do = OMe, R = Et; 1c, do = NMe(2), R = Me) with Ln[N(SiMe(3))(3)](3) yields highly volatile (sublimation < 100 degrees C/10(-)(3) Torr) and n-hexane-soluble homoleptic alkoxide complexes [Ln(OCR(2)CH(2)do)(3)] (2a-d, Ln = Y, Lu)…
Raman spectroscopy between 11 and 680 K was used together with room-temperature x-ray-diffraction experiments for structural studies of ferroelectric Nd-modified lead zirconate titanate ceramics at the morphotropic phase boundary. The Nd addition was found to have a strong effect on the balance between tetragonal and…
We have developed a new route to silicon-centered phthalocyanines and phthalocyanine-like compounds that is robust and flexible, and of considerable potential usefulness. This route entails insertion of silicon into the metal-free macrocycle. It has been developed in the course of preparing four new and two known meta…
The experimental fact that fused silica undergoes densification upon prolonged exposure to high-energy radiation is well documented. About 25 years ago, Primak Kampwirth [J. Appl. Phys.39, 5651 (1968)] reported extensive densification results in SiO2 obtained with neutron, electron, and γ-ray exposures. More recently,…
Abstract Ti-MCM-41 and Ti-MCM-48 mesoporous zeolites were prepared and investigations into the unprecedented use of these catalysts for the photocatalytic reduction of CO2 with H2O at 328 K were carried out. Ti-mesoporous zeolites exhibited high photocatalytic reactivity for the formation of CH3OH, its reactivity bein…
In recent experiments four-time correlation functions have been systematically measured for a polymer near the glass transition via methods of multidimensional NMR [A. Heuer et al., Phys. Rev. Lett. 75, 2851 (1995)]. In this paper a theoretical analysis of the information content of multitime correlation functions is…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHigh-Yield Macrocyclization via Glaser Coupling of Temporary Covalent Templated BisacetylenesSigurd Höger, Anne-Désirée Meckenstock, and Heike PellenView Author Information Max-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany Cite this: J.…
[ l ]-Lactide ([ l ]-LA)/ethylene oxide (EO) ring-opening copolymerizations were successfully carried out by using various catalysts including isobutylaluminoxane (IBAO), in situ AlR 3 ·0.5H 2 O systems (R = ethyl, isobutyl) and Sn−Al bimetallic catalysts. Analysis of products by 1 H NMR showed that methanol insoluble…
Recently a small amount of locally reversible melting was observed in semicrystalline poly(ethylene terephthalate) during temperature-modulated differential scanning calorimetry (TMDSC). To further study the reversibility of melting, poly(oxyethylene) (POE) is analyzed. Low molar mass POE is known to be able to form e…
Current theoretical models for the surface behavior of polymers have stressed the importance of several factors such as the chain length ( r ), local chain stiffness, and the surface energy difference between chain ends and middle segments, χ s . Here we assert that the critical parameter, which is affected by all of…
The magnetic properties of two series of dinuclear complexes, and one trinuclear complex, have been examined as a function of the bridging pathway between the metal centers. The first series of dinuclear complexes is [{Mo(V)(O)(Tp)Cl}(2)(&mgr;-OO)], where "OO" is [1,4-O(C(6)H(4))(n)O](2)(-) (n = 1, 1; n = 2, 3), [4,4'…
Abstract Conductive polymer composites were prepared by sintering a mixture of ultrahigh molecular weight polyethylene (UHMWPE) powder and carbon black. Two processing parameters—time and temperature—were shown to have a notable effect on the resistivity of the composites. The relationships between the processing para…