Materials Literature
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Femtosecond measurements of transient absorption, bleach, and stimulated emission are used to study the excited-state dynamics of phthalocyanine tetrasulfonate (PcS 4 ) and zinc phthalocyanine tetrasulfonate (ZnPcS 4 ) in solution. In water the excited-state decay process is fast and dominated by energy relaxation due…
A series of layered magnesium organosilicate nanocomposites that contain covalently linked organic functionalities have been prepared by a one-step, direct synthesis procedure. The in situ reactivity of organic moieties (e.g., phenyl, thiol) within the layered inorganic−organic nanocomposites, as well as the potential…
Blends of synthetic atactic poly(3-hydroxybutyrate) (a-PHB) with a natural bacterial isotactic copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV) containing 10 mol % of 3HV units were prepared using a simple casting procedure. In the range of compositions explored (10−50% a-PHB), blends of bacterial PHBV and…
The phenomenological boundary conditions for the envelope wave function, which is applicable for contacts of semiconductors with the rather different crystal symmetry are proposed. It is shown that the boundary conditions are determined by the number of real values, which are independent of the electron energy. The nu…
A simple model of polymeric relaxation, associated with the electrochemical switching of polypyrrole films between their reduced (insulating) and oxidized (electronically conducting) states, offers a reasonably precise description of the form of chronoamperograms obtained after previous subjection of the polymer film…
The synthesis and characterization of a family of well-defined liquid crystal−coil (LC−coil) diblock copolymers have been carried out. The block copolymers in this study have been designed to have nearly identical molecular weight azobenzene-containing LC blocks in order to eliminate possible variations in LC behavior…
The novel monovinyl-functional silsesquioxane cage 1-(9-decenyl)-3,5,7,9,11,13,15-heptaethylpentacyclo[9.5.1.1 3,9 .1 5,15 .1 7,13 ]octasiloxane has been prepared and copolymerized with ethene and propene. The monovinyl-functional spherosiloxane was obtained from the octahydridosilsesquioxane (HSiO 3/ 2 ) 8 via hydros…
Aggregation in the nondoped polyaniline, emeraldine base (EB), as observed by GPC in a N -methyl-2-pyrrolidinone (NMP) solution, was found to be closely related to the fraction of the imine nitrogen atoms in the nondoped polymer, i.e., to the oxidation state of the polymer. As EB was reduced to leucoemeraldine base (L…
Dielectric, ferroelectric and piezoelectric pŕoperties of a BNT-based solid solution, (1-x)(Bi1/2Na1/2)TiO3-xNaNbO3, that is, Bi(1-x)/2Na(1+x)/2 Ti1-x Nb x O3 (BNTN-100x), are studied from the viewpoint of a new group of lead-free piezoelectric ceramics. The conventional ceramic fabricating technique was used to prepa…
The corrosion behavior of copper in aqueous solutions of different pH values was investigated using electrochemical and surface analysis methods. It was shown that the corrosion mechanism changed with pH and was associated with morphology of the surface films formed. In solution of pH 3, the copper surface was covered…
The syntheses of two new derivatives of 3,4-ethylenedioxythiophene (EDOT), specifically 5-octyldioxeno[2,3- c ]thiophene (EDOT-C 8 ) ( 2 ) and 5-tetradecyldioxeno[2,3- c ]thiophene (EDOT-C 14 ) ( 3 ), and their polymers are reported in this paper. Cyclic voltammetry of 2 and 3 in 0.1 M TBAP/CH 3 CN show irreversible m…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSelective Catalytic Hydroxylation of a Steroid by an Artificial Cytochrome P-450 EnzymeRonald Breslow, Xiaojun Zhang, and Ying HuangView Author Information Department of Chemistry, Columbia University New York, New York 10027 Cite this: J. Am. Chem. Soc. 1997, 119, 19,…
Polycatenar mesogens have a shape intermediate between classical rod‐like and disc‐like liquid crystals which allows practically all the mesomorphic symmetrics to be obtained with the same molecular core by varying the temperature or the number and position of grafted chains (see Figure: R = H(CH 2 ) n O). The synthes…
Hexagonally closed packed monolayers of colloids have found more and more applications, e.g. as lithographic masks. The monolayers are usually produced with the help of a self-organizing process where a suspension of colloids is applied to the desired substrate and left to dry. This method requires a good wettability…
Low-rate dynamic contact angles and static advancing contact angles of 13 liquids were measured, respectively, by axisymmetric drop shape analysis (ADSA) and a conventional goniometer technique, on two copolymers, poly(propene- alt - N -( n -propyl)maleimide) and poly(propene- alt - N -( n -hexyl)maleimide); both have…
High‐density nickel–dispersed‐alumina (Al 2 O 3 /nickel) composites with superior mechanical properties were obtained by the hydrogen reduction and the hot pressing of alumina–nickel oxide (Al 2 O 3 /NiO) mixed powders. The mixtures were prepared by using NiO or nickel nitrate (Ni(NO 3 ) 2 · n H 2 O) as a dispersion s…
The first mesoporous materials (pore diameter between 20 and 100 Å) were discovered just five eyars ago. A new approach to mesoporous materials by direct templating of lyotropic liquid crystals is reviewed and compared with strategies reported previously. The direct templating method is shown to be very verstile. It i…
This paper describes the tensile, impact, flexural properties and aging behavior of short banana fiber reinforced polyester composites with special reference to the effect of fiber length and fiber content. Maximum tensile strength was observed at 30 mm fiber length while impact strength gave the maximum value for 40…
Multilayer thin films comprised of sequentially adsorbed layers of partially doped polyaniline and a polyanion, sulfonated polystyrene, were fabricated via the use of a simple layer-by-layer molecular-level processing scheme. Using this simple multilayer polymer adsorption process, uniform thin films of polyaniline in…
The electronic dynamics of gold nanocrystals, passivated by a monolayer of alkylthiol(ate) groups, were studied by transient spectroscopy after excitation with subpicosecond laser pulses. Three solution-phase gold samples with average particle size of 1.9, 2.6, and 3.2 nm with size distribution less than 10% were used…