Methyl-, vinyl-, and hydride-terminated polymers of the heterocyclic monomer, 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane (-ME) were prepared by sulfuric acid-catalyzed, ring-opening equilibration with the end-capping agents hexamethyldisiloxane (MM), divinyltetramethyldisiloxane (MM), and tetramethyldisiloxane (MM), respectively. The molecular weights of the polymers were controlled by adjusting the ratio of monomer to end-capping agent. All of these polymers are oils and exhibit molecular weight-dependent viscosities that are qualitatively similar to those of polydimethylsiloxane (PDMS)-based analogs prepared by the same reaction using octamethylcyclotetrasiloxane (D) instead of -ME.
View Article and Find Full Text PDFCross-linked polydimethylsiloxane (PDMS) is simultaneously water-repellent and highly permeable to water vapor. Unfilled and silica-free cross-linked PDMS films of variable thickness (8-160 µm) are prepared and their water vapor transmission rates and permeability values are determined. Vapor transmission rate increases as membrane thickness decreased from 160 to 15 µm, but does not increase further when the film thickness is decreased to 8 µm.
View Article and Find Full Text PDFSurfaces that exhibit the reactivity of silica toward surface modification (silanol condensation) were prepared by treating thin films and particles of poly(methylsilsesquioxane) with aqueous potassium persulfate at elevated temperature. Parallel experiments were carried out using a highly cross-linked poly(dimethylsiloxane). Advancing (θ) and receding (θ) water contact angles for all of these oxidized surfaces were θ/θ = ∼10/∼0°, and these low values remain unchanged for months.
View Article and Find Full Text PDFDifflugia are testate amoebae that use particulate inorganic matter to build a protective shell (generally called a test or theca). Difflugia globulosa were grown both in culture containing only naturally occurring theca-building materials and under conditions where synthetic particles were present also. The presence of monodisperse Stöber silica microspheres of 1, 3, and 6 μm in diameter or 4 μm polystyrene spheres dramatically increased the rate of Difflugia growth, and foreign microspheres became the overwhelmingly dominant construction material.
View Article and Find Full Text PDFVisible light induces switching of surface chemical patterns based on hybrid gels of thermally responsive poly(N-isopropyl acrylamide) copolymer networks containing iron oxide nanoparticles. The swelling of these hybrid gels is reduced upon illumination (see picture), allowing controlled unfolding of creased features formed owing to an elastic surface instability.
View Article and Find Full Text PDFSilicon/silicon dioxide surfaces containing 3 μm (width) × 6 μm (length) × 40 μm (height) staggered rhombus posts were prepared using photolithography and hydrophobized using a perfluoroalkyl-containing monofunctional silane. These surfaces exhibit water contact angles of θ(A)/θ(R) = 169°/156°. Water drops come to rest on a carefully aligned horizontal sample but roll when the surface is tilted slightly.
View Article and Find Full Text PDFFerrofluids based on oleate-stabilized nanoparticulate magnetite in cyclic olefin carrier solvents were prepared. Puddles of fluids containing 20-70 wt % magnetite in 1,5-cyclooctadiene or dicyclopentadiene can be moved or positioned on surfaces or in vessels with moderate magnetic fields (inexpensive NdFeB magnets). The surfaces of puddles with concentrations >40 wt % distort in response to magnetic fields applied perpendicular to the puddle surface and exhibit pointed liquid asperities.
View Article and Find Full Text PDFJ Environ Sci (China)
July 2016
The magnesium sea water battery belongs to a kind of reserved battery, which takes the active metal such as magnesium alloy as the anode based on the sea water as the electrolyte. Experiments of magnesium alloy sea water battery were carried out and its electrochemical performance was studied. Thin sheets of Mg-Al-Zn and Mg-Mn series of magnesium alloy were fabricated and used as the anode of magnesium battery.
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