Materials Literature
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Poly(oxyethylene)-dicarboxylic acids were obtained in high yields by room temperature oxidation of poly(ethylene glycol)s of molecular weights in the 4000–100,000 range using Jone's reagent (CrO3 and H2SO4) as the oxidizing agent. Oxidation by-products from the reaction mixture were eliminated by adsorbing chromium sa…
The effects of shear flow, temperature, and gel concentration on the rheological behavior of the ultrahigh-molecular-weight polyethylene (UHMWPE) gel in gel spinning process were investigated. The gel point was determined using parallel plate rheometry in rotation mode with controlled stress. Likewise, the flow curves…
Two crystalline structures for nylon 5,6 have been studied by transmission electron microscopy, electron diffraction, and X-ray diffraction. A γ form or an α-like phase can be obtained as a function of the method used to prepare the sample. Structural modeling and energy calculations have been carried out for the seco…
The photooxidative degradation of a TiO 2 -blended poly(vinyl chloride) (PVC) film and other PVC specimens was carried out under UV light and under solar exposure to test the feasibility that such polymeric materials can be mineralized. The effects of the degree of polymerization and the presence of a plasticizer ( o…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTDirect Evidence for Confinement of Junctions to Lines in an 3 Miktoarm Star Terpolymer Microdomain StructureStella Sioula, Nikos Hadjichristidis, and Edwin L. ThomasView Author Information Department of Chemistry, University of Athe…
The applicability of the Hoffman−Weeks (HW) linear extrapolation for the determination of equilibrium melting temperatures of polymers is critically reviewed. In the first paper of this series, it is shown that the linear extrapolation of observed melting temperatures cannot, in general, provide a reliable estimate of…
The Rayleigh-Rice (R-R) vector perturbation theory agrees well with experimental wide-angle scatter measurements from 'smooth' surfaces for arbitrary incident angles. However, not all applications of interest satisfy the smooth surface approximation. The Beckmann-Kirchoff (B-K) scalar diffraction theory of surface sca…
The interaction of tungsten with hydrogen peroxide was studied by Raman spectroscopy and electrochemical measurements. We found that W catalyzes the decomposition of peroxide into its ion, while the native oxide of W becomes increasingly hydrated and soluble. The decay of the peroxide concentration upon immersion of W…
Abstract
Dendritic polypyridines were analysed by laser desorption (LD) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. For all the compounds examined, readily detectable cationized molecular species have been obtained under LD conditions, while for MALDI a strong matrix effect has been found, leadin…
The effect of tacticity on the thermal degradation behavior under nitrogen of poly(methacrylic acid)s has been investigated. The structural changes occurring in the polymer chains during the first of the two stages of decomposition, at temperatures lower than 300 °C, were followed by FTIR and NMR. In this stage, the d…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDiscotic Liquid Crystals from a Bis-Pocketed PorphyrinBimal R. Patel and Kenneth S. SuslickView Author Information Department of Chemistry University of Illinois at Urbana-Champaign 600 S. Mathews Avenue, Urbana, Illinois 61801 Cite this: J. Am. Chem. Soc. 1998, 120, 4…
F420H2:NADP oxidoreductase is found in methanogenic, sulfate-reducing and halophilic archaea and also in some bacteria. The putative gene encoding the enzyme was cloned from Methanobacterium thermoautotrophicum (strain Marburg) and heterologously expressed in Escherichia coli. The overproduced active enzyme was purifi…
The synthesis of a series of new high-barrier poly(hydroxy amide ethers) is described. The polymers are formed by the reactions of aromatic diglycidyl ethers, with N, N ‘-bis(3-hydroxyphenyl)adipamide, HOC 6 H 4 NHCO(CH 2 ) 4 CONHC 6 H 4 OH, at 140−160 °C in propylene glycol monophenyl ether solvent using ethyltriphen…
Protein S, a two-domain spore coat protein from Myxococcus xanthus, is structurally related to eye-lens Pr crystallins. No natural monomeric one-domain member of this protein superfamily is known. To determine the stability of the single domains and to explain the ubiquitous domain duplication, the isolated domains of…
Abstract
The self-diffusion properties of a poly(styrene- b -isoprene) diblock copolymer ( M PS = 10000, M PI = 13000) in a lamellar microstructure have been determined by forced Rayleigh scattering. Diffusion coefficients along the lamellar interface ( D par ) and through the layers ( D perp ) were resolved. The lamellae were…
The cuboctameric silsesquioxane silanol ( c -C 5 H 9 ) 7 Si 8 O 12 (OH) has been applied as a model support for silica-grafted olefin polymerization catalysts. Complexes of the type Cp‘‘[( c -C 5 H 9 ) 7 Si 8 O 13 ]TiX 2 (Cp‘‘ = 1,3-C 5 H 3 (SiMe 3 ) 2; X = Cl, CH 2 Ph) form active α-olefin polymerization catalysts.
The ground- and excited-state properties of a series of p -phenylene-linked porphyrin dimers have been examined using a variety of static and time-resolved spectroscopic techniques. The dimers consist of a zinc porphyrin and a free base (Fb) porphyrin (ZnFbΦ), two zinc porphyrins (Zn 2 Φ), or two Fb porphyrins (Fb 2 Φ…
A high resolution optical method was used to acquire contact angle−velocity data for hexadecane and octamethylcyclotetrasiloxane (OMCTS) advancing and receding on a smooth, virtually homogeneous fluorinated surface. The predictive abilities of the hydrodynamic, molecular−kinetic and combined molecular−hydrodynamic mod…