Materials Literature
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A new prediction model for the autocatalytic random hydrolysis of aliphatic polyesters is proposed. The model predicts changes in the number- and weight-average degrees of polymerization. The model enables to avoid certain errors liable to occur in the estimation of hydrolysis with only the number-average molecular we…
The identification of a window of viscosities of poly(tetrafluoroethylene)s is described that permits standard melt-processing of this unique polymer into mechanically coherent, tough objects a polymer that, heretofore, has been characterized as “intractable” and “not melt-processable”.
We present results of a systematic study on the sorption- and phase behavior of nitrogen, argon, and krypton at 77 and 87 K in different pristine mesoporous MCM-48 silica phases (BJH pore diameters 2−3 nm) and MCM-48 silica/iron(III) host compound, which consists of two interwoven, but unconnected three-dimensional po…
Methane and krypton adsorption measured on single-walled nanotubes at 78.7 and 77.3 K, respectively, give rise to stepwise isotherms, representative of the adsorption on two types of comparatively uniform patches during the first stages of the adsorbate condensation. The values of the methane isosteric heat of adsorpt…
In this paper, Novozyme-435-catalyzed ω-pentadecalactone and ω-pentadecalactone/ε-caprolactone polymerizations were investigated. Novozyme-435-catalyzed ω-pentadecalactone polymerizations were studied in bulk and at ω-pentadecalactone-to-toluene ratios from 1:1 to 1:10 (wt/vol). By carrying out polymerizations with ω-…
Barite particles with a rich variety of well-defined morphologies have been synthesized by using double-hydrophilic block copolymers (which consist of a hydrophilic solvating block and a hydrophilic binding block) as crystal growth modifiers to direct the controlled precipitation of barium sulfate from aqueous solutio…
Colloidal dispersions of polymer−silica nanocomposite particles were synthesized in high yield by homopolymerizing 4-vinylpyridine (4VP) in the presence of an ultrafine silica sol using a free-radical initiator in aqueous media at 60 °C. Copolymerization of 4VP with methyl methacrylate and styrene also produced colloi…
We demonstrate that X-ray irradiation can be used to induce an insulator-metal transition in Si-doped Al$_{0.35}$Ga$_{0.65}$As, a semiconductor with {\it DX} centers. The excitation mechanism of the {\it DX} centers into their shallow donor state was revealed by studying the photoconductance along with fluorescence. T…
A new series of oxides Ca 3 - x Bi x Co 4 O 9+ δ, ( x = 0.0−0.75) with Ca 2 Co 2 O 5 -type structures were synthesized, and their structures, electrical properties, Seebeck coefficients, and thermal conductivities were measured. The values of Seebeck coefficients of the new oxides are all positive, showing that they a…
The glass transition temperature of polystyrene and poly(methyl methacrylate) films on polar and nonpolar substrates was measured as a function of thickness using a thermal probe in contact with a polymer film. Using a technique called local thermal analysis, heat loss into the film was monitored as the temperature of…
The interaction of hydrazine with kaolinite was studied using a combination of infrared (IR) spectroscopy, inelastic neutron scattering (INS), and X-ray powder diffraction. Under ambient temperature and pressure conditions, anhydrous hydrazine is readily intercalated into the interlamellar region of kaolinite resultin…
The Raman scattering spectra of Ba 3 MoNbO 8.5 and Ba 7 Nb 4 MoO 20, two cation-deficient perovskite-like oxides, are presented for the first time and analyzed in an attempt to confirm the distribution of octahedra and tetrahedra proposed in recent structural investigations. The Raman spectra are discussed in relation…
Bis(N-ethylideneethanamine)ruthenium(ii) porphyrins, [Ru11(Por)(N(Et)=CHMe)2] (Por=TTP, 4-Cl-TPP), were prepared by the reaction of dioxoruthenium(VI) porphyrins with triethylamine in approximately 85% yields. The reaction between dioxoruthenium(VI) porphyrins and benzophenone imine afforded bis(diphenylmethyleneamido…
Unusual thermal robustness is exhibited by a homoleptic ytterbium complex, which sublimes intact at temperatures in excess of 500 °C/760 Torr. Employment of a (N)-nPr substituted ketoiminate ligand provides notable metal encapsulation and ensures substantial air stability and vapor-phase integrity. The octahedral coor…
A new series of homo- and heterometallic oxalato-bridged dinuclear compounds of formulas [Et4N]4[MM'(ox)(NCS)8] ([Et4N]+ = [(C2H5)4N]+; ox = C2O4(2-)) with MM' = Cr(III)-Cr(III) (1), Fe(III)-Fe(III) (2), and Cr(III)-Fe(III) (3) is reported. They have been structurally characterized by infrared spectra and single-cryst…
The design, synthesis, and solution properties of six constitutional isomers of dendrimer-like star polymers is described. Each of the polymers have comparable molecular weights (∼80 000), narrow polydispersities (<1.19) and an identical number of branching junctures (45) and surface hydroxyl functionalities (48). The…
Three C 2 -symmetric (10 R,11 R )-diethyl substituted dibenzosuberane (DBS)-based helicenes with varying steric and conjugation demands of their bottom fragments were synthesized. The X-ray analyses of their precursors-episulfides reveal the preferred conformation of the DBS skeleton possessing equatorially oriented e…
When the dimensions of matter are reduced to the nanometer scale and beyond, strange properties often emerge. In their Perspective, Tosatti and Prestipino discuss the weird gold nanowire structures reported by Kondo and Takayanagi. They explain why the wires may be helical and only form certain "magic" sizes. Other me…
The reorientation dynamics of local tangent vectors of chains in isotropic amorphous melts containing semiflexible model polymers was studied by molecular dynamics simulations. The reorientation is strongly influenced both by the local chain stiffness and by the overall chain length. It takes place by two different su…
The spray pyrolysis technique has been employed to prepare uniform, large-area thin-film coatings of PbS on glass and on fluorine-doped tin oxide (FTO) conducting substrates at various substrate temperatures. Growth of polycrystalline PbS films occurred at a lower temperature ( T S = 275 °C) on conducting substrate th…