Materials Literature
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Hydrophobicity of a “water-tolerant” solid acid, Cs 2.5 H 0.5 PW 12 O 40, has been investigated by adsorptions of water and benzene. One water molecule was adsorbed irreversibly at 298 K per one proton of Cs 2.5 H 0.5 PW 12 O 40 as well as H−ZSM-5 (Si/Al = 40), while H 3 PW 12 O 40 formed a stable hexahydrate. From th…
Isotactic polypropylene (iPP) samples, quenched and then annealed at 70°C, 80°C, 110°C, 140°C, and 150°C, were investigated by X-ray diffraction. The transition from the quenched form (smectic) to the well-crystallized one is analyzed to explain better the morphological-structural changes that occur by annealing. For…
Crystallization and melting of a copolymer depend on both intrachain and interchain distributions of noncrystallizable comonomer. Hydrogenated polybutadiene (HPB) is a model ethylene-butene (EB) random copolymer with known intrachain distribution and no interchain distribution of branching. Differential scanning calor…
Twelve viologens, i.e., 4,4′-bipyridinium derivatives 1 – 12, were examined for their use as electrochromic material when attached to nanocrystalline titanium dioxide thin-film electrodes. Eight of these (1 – 4, 7 – 8, 10, and 12) are new, and their synthesis is included. The modifier compounds consist of one to four…
Ferricyanide oxidation of 1,4,5,6-tetrahydro-2,4-dimethyl-6-(2'-pyridyl)-1,2,4,5-tetrazin-3(2H)-one (pvdH3) produces the stable chelating free radical 1,5-dimethyl-3-(2'-pyridyl)-6-oxoverdazyl (pvd) as an orange solid. Combination of group 12 metal halides with the ligand pvdH3 in acetonitrile results in precipitation…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHydroformylation Reactions Using Recyclable Rhodium-Complexed Dendrimers on SilicaS. Christine Bourque, Howard Alper, , and View Author Information Department of Chemistry, University of Ottawa 10 Marie Curie, Ottawa, Ontario, Canada K1N 6N5 DuPont Central Research & D…
The silation of silica with hexamethyldisilazane (HMDS) was examined over the temperature range 150−450 °C. The products and sequence of the reactions at the silica surface were determined. The major products are hexamethyldisiloxane (HMDSO) and ammonia, with lesser amounts of nitrogen and methane. No methane is produ…
The "electrochemical/chemical method" (or "E/C method") is a new wet chemical method for synthesizing semiconductor quantum dots on graphite surfaces. The E/C synthesis of quantum dots composed of the generic semiconducting salt, MX, typically involves three steps: (1) electrochemical deposition of nanoparticles of th…
Thin films of a biopolymer chitosan (CHIT) were cast on glassy carbon electrodes, modified by grafting Lucifer Yellow VS dye (LYVS) onto chitosan chains, and cross-linked with glutaric dialdehyde (GDI). The ion-transport and ion-exchange properties of such polymeric structures (CHIT, CHIT-LYVS, CHIT-LYVS-GDI) were stu…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA S = 7 Ground Spin-State Cluster Built from Three Shells of Different Spin Carriers Ferromagnetically Coupled, Transition-Metal Ions and Nitroxide Free RadicalsKira E. Vostrikova, Dominique Luneau, Wolfgang Wernsdorfer, Paul Rey, and Michel VerdaguerView Author Inform…
We present high-quality numerical calculations of the exciton center-of-mass dispersion for GaAs/AlGaAs quantum wells of widths in the range 2-20 nm. The k.p-coupling of the heavy- and light-hole bands is fully taken into account. An optimized center-of-mass transformation enhances numerical convergence. We derive an…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHierarchically Imprinted Sorbents for the Separation of Metal IonsSheng Dai, M. C. Burleigh, Y. H. Ju, H. J. Gao, J. S. Lin, S. J. Pennycook, C. E. Barnes, and Z. L. XueView Author Information Chemical Technology and Solid State Divisions Oak Ridge National Laboratory…
Recently, we outlined a scheme to investigate the effects of compositional order on the magnetocrystalline anisotropy of alloys from a first-principles electronic structure point of view \{Phys. Rev. Lett. {\bf 83}, 5369 (1999)\} and showed that compositional order enhances the magnitude of magnetocrystalline anisotro…
The large surface density changes associated with the (100) noble metals surface hex-reconstruction suggest the use of non-particle conserving simulation methods. We present an example of a surface Grand Canonical Monte Carlo applied to the transformation of a square non reconstructed surface to the hexagonally covere…
We have studied the microdomain morphology of thin ABC triblock copolymer films supported by a solid substrate. The films were exposed to various solvent vapors, and the effect of the solvent removal speed on the resulting morphologies is investigated. Slow solvent extraction rates lead to a parallel alignment of lame…
Poly(methyl methacrylate–maleic anhydride) [P(MMA–MAn)] with active groups, anhydrides, was synthesized by radical copolymerization. Using P(MMA–MAn) as a basic polymer, the P(MMA–MAn)/SiO2 hybrid materials were obtained by a sol–gel process in different ways. The structures of the materials were characterized by IR s…
To investigate the effect of a flame retardant on PC/ABS alloy systems, a reactive-type brominated epoxy resin was used as a flame retardant, and mixed with PC/ABS at various amount using a twin-screw extruder. The rheological, morphological, mechanical, and thermal properties were investigated as a function of acrylo…
The distinct electronic states of assemblies of metallic quantum dots are discussed in a simple approximation where each dot is mimicked as an "atom" that carries one valence electron. Because of their large size, the charging energy of the dots, I = energy required to add another electron, is much smaller than for or…
The thermal and flame-retardant properties of homo- and copolyimides were evaluated. Those containing sulfone linkages in the backbone were found to be more flame retardant. Both properties were dependent on the composition. A polyimide/silica nanocomposite was obtained through sol–gel processing. The effects of the a…
Two novel series of poly(arylidene-ether)s and copoly(aryl-idene-ether)s were synthesized by polycondensation of 4,4′-diformyl-α,ω-diphenoxyalkane and 4,4′-diformyl-2,2′-dimeth-oxy-α,ω-diphenoxyalkane with cyclohexanone and/or cyclo-pentanone. The inherent viscosity of the polymers and copolymers thus prepared were in…