Materials Literature
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Abstract Four photoreactive coumarin derivatives were successfully synthesized from 7‐hydroxy‐coumarin and 7‐hydroxy‐4‐methylcoumarin, i.e., 7‐propionyloxy‐4‐methylcoumarin (M 1 ), 7‐palmitoyloxy‐4‐methylcoumarin (M 2 ), 7‐propionyloxycoumarin (M 3 ), and 7‐palmitoy‐loxycoumarin (M 4 ). Reversible photodimerization (3…
Abstract Six different polyesters ( 6a–6c and 7a–7c ) were prepared by the bulk polycondensations of the respective combinations of 1,4:3,6‐dianhydro‐D‐glucitol ( 3 ) and 1,4:3,6‐dianhydro‐D‐mannitol ( 4 ) with succinyl dichloride ( 5a ), glutaryl dichloride ( 5b ), and adipoyl dichloride ( 5c ) at 140–180°C. Polyeste…
Abstract The graft copolymerization of acrylonitrile (AN) onto a styrene‐maleic acid copolymer (SY‐MAc) with ceric ammonium nitrate (CAN) as a redox initiator in an aqueous medium has been studied. The effects of various reaction parameters, including reaction time and temperature, concentrations of initiator, nitric…
Abstract Typical polypropylene fibers for use in light nonwoven fabrics were produced in a full scale compact‐spinning line. Molecular weight distribution (MWD), extrusion temperature, draw‐down ratio, and draw ratio were varied. The fibers were thermally bonded (welded) into nonwoven fabrics, at different bonding tem…
Abstract Polycondensation of 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA) with 3,3′‐diaminobenzidine (DAB) and 3,3′4,4′‐tetraaminodiphenyl ether (TADPE), respectively, in N,N′ ‐dimethylacetamide (DMAc) at room temperature was found to produce high‐viscosity polybenzimidazobenzophenanthroline (PBIPA) precursor…
Abstract A multicompartment model is proposed for a semibatch melt polycondensation of poly(ethylene terephthalate) in a rotating disk polymerization reactor and compared with laboratory experimental data. The reactor is a horizontal cylindrical vessel with a horizontal shaft on which multiple disks are mounted. The r…
Abstract Effects of composition, compatibilization, and blending procedure on oxygen barrier properties of injection‐molded polypropylene/polyamide 6 blends were investigated. The main attention was paid to the relationships between oxygen permeability, mechanical properties, and blend morphology. The effect of the po…
Abstract Brief thermal curing of papers treated with an aqueous solution of polyfunctional carboxylic acids and NaH 2 PO 4 imparts substantial wet strength to the papers. The effectiveness of such carboxylic acids increases with their functionality in the order 1,2,3,4‐butanetetracarboxylic acid (BTCA) > tricarball…
Abstract This work examines the properties of starch esters for their possible application as environmentally degradable thermoplastics. The rheological, thermal, and mechanical properties of a series of fatty‐acid esters of high‐amylose starch (as well as the effects of adding plasticizer on some selected properties)…
A micro-Raman study of polydioxolane (PDXL)/NaClO4 and PDXL/LiClO4 polymeric electrolytes has been carried out in a wide range of salt concentration, at room temperature. The ion–ion interactions and the precipitation of salt microcrystals in the host polymer have been evidenced by means of a line shape analysis of th…
We present a specific geometric description of the approximant phases in quasicrystals using a classification based on symmetry arguments. We derive the 'shear' technique as a special case of this description and discuss the cases of periodic approximants. Observing that all presently known approximant phases have hig…
Porous GaP layers prepared by electrochemical anodization of (100)-oriented bulk material was found to exhibit blue and ultraviolet photoluminescence when excited by a KrF excimer laser. The energy position of the UV luminescence band (3.3 eV at 300 K) is explained on the basis of charge carrier confinement in crystal…
We demonstrate the preparation of narrow-band porous-silicon reflectors integrated on porous-silicon layers by electrochemical etching. By carefully tuning the resulting photon cavity mode around the maximum of the porous silicon photoluminescence, we have obtained both a narrowing and enhancement of the emission line…
We present an X-ray absorption spectroscopy study of Ni c Mg 1-c O (0.01<or=c<or=1) solid solutions on the Ni K edge. The analysis of XANES and EXAFS regions allowed us to obtain the following results. The nickel ions are located in a distorted environment and shift upon dilution to the off-centre positions. In the fi…
We present the first $^{13}\mathrm{C}$ NMR measurements carried out in the superconducting state of a two-dimensional organic superconducting single crystal. Spin lattice relaxation rate and Knight shift are reported for magnetic fields parallel and perpendicular to the conducting layers. For perpendicular fields, the…
Theoretical results for the temperature dependence of the thermal expansion coefficient for 3C–SiC are reported using a phenomenological lattice dynamical theory in the quasiharmonic approximation. The linear thermal expansion coefficient α of 3C–SiC exhibits a variation with temperature much like that of the specific…
We develop rigorous bounds on the effective thermal conductivity ${\ensuremath{\sigma}}_{e}$ of dispersions that are given in terms of the phase contrast between the inclusions and matrix, the interface strength, volume fraction, and higher-order morphological information, including interfacial statistics. The new bou…
Materials with desirable properties may be created through control of crystal size and shape and assembly of such crystals into more complex arrangements. In his Perspective, Heath discusses recent work reported in this issue by Murray et al . ( p. 1335 ) in which nanocrystals of cadmium selenide were formed into orde…
The self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superlattices (colloidal crystals) is demonstrated. The size and spacing of the dots within the superlattice are controlled with near atomic precision. This control is a result of synthetic advances that provide CdSe nanocr…
Following Sham and Rice [L. J. Sham, T. M. Rice, Phys. Rev. 144 (1966) 708] the correlated motion of particle-hole pairs is studied, starting from the general two-particle Greens function. In this way we derive a matrix equation for eigenvalues and wave functions, respectively, of the general type of collective excita…