Surface modification by adsorption of macromolecules; organosilane/metal oxide chemistry
Abstract (Summary)Poly(trifluoroethylene) (PF3 E) irreversibly adsorbs to oxidized silicon and covalently attached amine monolayers supported on silicon, producing hydrophobic thin films in the thickness range of 8-40 Ã?. The ultra-thin films of adsorbed PF3 E were characterized here by means of contact angle, ellipsometry and X-ray photoelectron spectroscopy (XPS). Adsorption conditions such as reaction time, polymer concentration and solvent composition were also investigated. The adsorption behavior of PF3 E can be explained by its ability to crystallize and form hydrogen bonds with proton acceptors, due to highly polar C-H bonds throughout the backbone. The hydrogen bonding - directed layer-by-layer assembly technique was used to build multilayers of poly(trifluoroethylene) (PF3 E) and poly(4-vinylpyridine) (P4VP) from methanol solution. It was difficult to build up layers subsequent to the second layer, due to the replacement of an already formed layer by the adsorbing polymer. The remainder of this thesis describes the modification of metal oxide surfaces with organosilanes. Silicon-supported titanium oxide is modified by the reaction of hydridosilane (R3-n SiHn+1 ) in the vapor phase and in heptane solution at elevated temperatures. Surfaces are characterized by contact angle measurements and XPS. The preparation of hydrophobic alkylsiloxane layers on chromium surfaces by reaction of organosilanes R 3-n SiXn+1 (where X=Cl, OEt and H) was examined under two conditions: (1)Ã?Â in the vapor phase and (2)Ã?Â in toluene in the presence of ethyldiisopropylamine (EDIPA) using chloro- or ethoxysilanes, or in heptane using hydridosilanes. Surfaces were again characterized by contact angle analysis and XPS. Silicon-supported alkylsiloxane layers are prepared by the reaction of tri-n-hexylsilane and octylsilane in the vapor phase, in toluene and in ScCO2 at elevated temperatures, and octadecylsilane in the vapor phase and in toluene solution. It is shown that the layer structure depends on the reaction conditions. The kinetics of vapor phase reactions using tri-n-hexylsilane and octylsilane and ScCO2 phase reaction using octylsilane are described.
School Location:USA - Massachusetts
Source Type:Master's Thesis
Date of Publication:01/01/2006