Applied Materials And Methods For Surface Modification
Surface modification is very important in tailoring materials properties. Various methods and materials have been explored and developed to provide unique properties on different substrates for practical applications. One of the most effective methods is to use surface-grafting procedures to introduce functional coatings on various substrates. Here in this thesis, grafting techniques are applied to grow polymer brushes on substrates with selected surface morphologies, e.g. flat and spherical surfaces. By tailoring the functionalities of the polymers, desirable properties such as antifouling behavior and enhanced solubility can be specifically designed and achieved. These as-modified functional materials can be successfully applied to complex working environments, indicating the methods and materials can be used for additional promising surface modification processes. The first example is to functionalize reverse osmosis membranes with antifouling polymer brushes using a 'layer-by-layer' mediated method. This specific method not only protects the membrane surface from potential chemical damage, but also amplifies the reaction sites on the surface. Different antifouling polymer brushes were successfully grown on the flat membrane surfaces through both 'grafted to' and 'grafted from' approaches. The membrane exhibits improved antifouling properties against different kinds of bio-foulants with no change of water flux and salt rejection ratios. The second example is the synthesis of hybrid nanoparticles as potential tracers for enhanced oil recovery and carbon dioxide (CO2) sequestration. Fluorinated polymers were modified onto different nanoparticle spherical cores through a surface-initiated atomic transfer radical polymerization (SI-ATRP) reaction. Incorporation of fluorescent labels makes the nanoparticles easy to be detected. The as-prepared nanohybrids have diameters around 40 nanometers and the solubility of these nanoparticles in scCO2 has been significantly improved. Further application of the nanopraticles in diffusion tests shows that they can be applied as potential tracers in real geological oil fields. While surface-grafting techniques are one type of modification method, which in principal is to add coatigs on the substrates, another kind of modification methods is to remove coatings from a substrate using methods such as plasma or chemical etching. In this thesis, new etching processes are also investigated. Supercritical carbon dioxide is used as a processing medium to remove post-etch organic residue on silicon wafers and to etch titanium nitride (TiN) as well. scCO2 compatible quaternary ammonium salts were synthesized and applied with co-solvents to enhance the cleaning efficiency. Strong organic acids and peroxides, together with alcohols as stabilizers, were used to successfully etch TiN from silicon surfaces in both organic solvents and scCO2.
Ober, Christopher Kemper
Baird, Barbara Ann; Coates, Geoffrey
Chemistry and Chemical Biology
Ph.D. of Chemistry and Chemical Biology
Doctor of Philosophy
dissertation or thesis