Materials Literature
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The formation of continuous mesoporous silica films with large periodic cage and pore structures is reported here. The authors use low-cost commercially available triblock copolymers and poly(ethylene oxide) non-ionic surfactants as the structure-directing agents in conjunction with dip-coat processing. In the Figure…
We discuss the deformation of a curved interface between solid phases, assuming small strains in the bulk phases and neglecting accretion at the interfaces. Such assumptions are relevant to the deformation of solid microstructures when atomic diffusion and the formation of defects such as dislocations are negligible.…
The synthesis, spectroscopy, and fluorescence quenching behavior of pentiptycene-derived phenyleneethynylene polymers, 1 − 3, are reported. The incorporation of rigid three-dimensional pentiptycene moieties into conjugated polymer backbones offers several design advantages for solid-state (thin film) fluorescent senso…
Poly(acrylic acid)-silica composites have been prepared by two different methods and thermally characterized. The glass transition temperature (Tg) of the PAA-SiO2 system prepared by mixture method was found to be 120°C irrespective of the type and amounts of silica involved in this work. However, the Tg varied betwee…
A comparative study has been made of the crosslinking of plasticized PVC by grafting of γ-aminopropyltriethoxysilane (ASi) and sodium γ-mercaptopropyltrimethoxysilane (NaMSi) during processing. The influence of type of reagent and concentration, and the rheological behavior were investigated to obtain a crosslinked ma…
Nitric oxide is formed during the combustion of fossil fuels and is subsequently oxidized in the atmosphere to NO 2 . The increasing knowledge of pollution problems arising from NO x had led to the introduction of stringent environmental regulations concerning NO x emissions that in most cases, cannot be met by the on…
The essential work of the fracture (EWF) method was employed to determine the fracture performance of thermoplastic polypropylene (PP) elastomers. Three types of elastomeric polypropylene (ELPP) of homo- and copolymer nature based on different catalysts were involved in this study. Tests were carried out in both I and…
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…