Jill Fornalik

Organic Solvent-Dispersed TiO2 Nanoparticle Characterization

Anatase titanium dioxide nanoparticles are derivatized with the polymerizable reagent (3-methacryloxypropyl)trimethoxysilane to provide dispersions in organic solvent. The titania core particles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The organic component structures and thickness are elucidated using nuclear magnetic resonance (NMR), quasielastic light scattering (QELS), and size-exclusion chromatography (SEC). Thin, high-refractive-index coatings prepared from the organic dispersions are characterized by atomic force microscopy (AFM). The combination of microscopies, spectroscopy, light scattering, and separation techniques provides unique information on the structure, thickness, morphology, and size distributions of the surface-treated nanoparticles that is difficult to obtain by any single technique. The findings indicate titania platelets with a modal diameter of 9.8 nm and a thickness of approximately 1.5 nm. The particles are coated with a 1.5-1.9 nm thick organic ligand layer, and a substantial population of 2 nm siloxane oligomers is detected. The analytical methodology presented may also be useful for characterizing other anisotropic organic-inorganic nanoparticles and their dispersions.

Surface and bulk compositional characterization of plasma‐polymerized fluorocarbons prepared from hexafluoroethane and acetylene or butadiene reactant gases

The surface tension and surface and bulk composition of plasma-polymerized fluorocarbon films (PPFCs) prepared from hexafluoroethane (HFE) and either acetylene or butadiene reactant gases were determined. Increasing the HFE reactant gas content from 0 to 100% gave an increase in the amount of fluorine incorporated in the films and a shift to incorporation of more highly fluorinated species at the film surface, according to X-ray photoelectron spectroscopy (XPS ) data. Hydrogen levels in the films were determined by forward recoil spectrometry (FRS) and were shown to be inversely dependent on HFE concentration in the reactant gas feed and dependent on hydrocarbon co-reactant type. The compositional changes were mirrored by changes in the surface tension from 52 to 20 mN/m. XPS and surface tension results demonstrated that fluorine incorporation at the surface of the PPFCs is significantly reduced when butadiene, rather than acetylene, is used as a co-reactant gas with HFE. The differences are attributed to higher concentrations of hydrogen, which acts as a scavenger for reactive fluorine atoms and as an inhibitor in the CF x → CF x+1 reaction, and of carbon, decreasing the F/C ratio, when butadiene is used as the hydrocarbon source. Furthermore, potential changes in surface composition due to energetic ion bombardment are discussed. Three factors were suggested as strongly influencing the composition and the properties of the PPFCs: 1) the energy input into the plasma polymerization reaction, 2) the amount and type of fluorine scavenging reagent introduced with the HFE, and 3) the elemental composition of the reactant gases.

Spontaneous multiscale phase separation within fluorinated xerogel coatings for fouling-release surfaces.

Four-component xerogel films consisting of 1 mole-% n-octadecyltrimethoxysilane (C18) and 50 mole-% tetraethoxysilane (TEOS) in combination with 1–24 mole-% tridecafluoro-1,1,2,2-tetrahydrooctyltriethoxysilane (TDF) and 25–48 mole-% n-octyltriethoxysilane (C8) and a 1:49:50 mole-% C18/TDF/TEOS were prepared. Settlement of barnacle cyprids and removal of juvenile barnacles, settlement of zoospores of the alga Ulva linza, and strength of attachment of 7-day sporelings (young plants) of Ulva were compared amongst the xerogel formulations. Several of the xerogel formulations were comparable to poly(dimethylsiloxane) elastomer with respect to removal of juvenile barnacles and removal of sporeling biomass. The 1:4:45:50 and 1:14:35:50 C18/TDF/C8/TEOS xerogels displayed some phase segregation by atomic force microscopy (AFM) pre- and post-immersion in water. Imaging reflectance infrared microscopy showed the formation of islands of alkane-rich and perfluoroalkane-rich regions in these same xerogels both pre- and post-immersion in water. Surface energies were unchanged upon immersion in water for 48 h amongst the TDF-containing xerogel coatings. AFM measurements demonstrated that surface roughness on the 1:4:45:50 and 1:14:35:50 C18/TDF/C8/TEOS xerogel coatings decreased upon immersion in water.

Compositions and surface energies of plasma-deposited multilayer fluorocarbon thin films

Abstract Multilayer fluorocarbon/hydrocarbon/silicon films were deposited by using a radio-frequency plasma discharge onto stainless steel substrates in order to produce coatings with progressively lower surface energies. Surface energy was varied through the use of reactant gas mixtures of hexafluoroacetone (HFA) and 5–100% acetylene or butadiene. The surface energy and surface and bulk composition of the films were determined by means of contact angle measurements, X-ray photoelectron spectroscopy (XPS), forward recoil spectrometry (FRS) and Rutherford backscattering spectrometry (RBS). Variations in HFA/hydrocarbon reactant gas mixtures used for deposition of the fluorocarbon layer demonstrated that films with surface energies as low as 19 mN m −1 could be obtained. Increasing the ratio of HFA to hydrocarbon in the feed gas mixture gave films with higher fluorine content and lower surface energy, with acetylene giving films with lower surface energy and higher fluorine content than butadiene. The surfaces of the films were shown to be richer in fluorine than the bulk. The surface and bulk compositional differences were attributed to lower levels of ion bombardment experienced by the film surface. The final composition and properties of the multilayer structure were suggested to result from a balance of the distribution of radical species in the plasma and the dose of energetic ion bombardment at the growing film surface. For the fluorocarbon layer, these factors were determined by the amount and type of hydrocarbon in the feed gas and by the plasma deposition conditions.