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Surface functionalization: From polymers to ceramics
Described here are two methods for functionalizing the surfaces of multiple materials. It is often useful to modify only the surface of a material. Surface modifications described here concentrate on the application of ceramics such as diamond-like carbon (DLC) and silicon carbide as well as surface initiated polymerization from either anionic or catalytic mechanisms. The syntheses of soluble preceramic polymers to DLC are shown. The synthesis of poly(hydridocarbyne) is simple and gives high yields. The polymer is soluble in tetrahydrofuran and other common organic solvents, which enables films and moldings to be formed from it. Ceramic resulting from the pyrolysis of poly(hydridocarbyne) is the purest DLC formed from any polymeric precursor found in the literature. The DLC ceramic films produced from the poly(hydridocarbyne) precursor are extremely smooth, continuous and impurity free. This polymeric precursor offers a potential alternative to the CVD process for making DLC films. In the current work a synthesis for high molecular weight precursor for SiC has been demonstrated. The synthesis of poly(methylsilyne) (PMSi) is a simple synthesis and gives high yields. The polymer is non-pyrophoric, which is unique among high yield stoichiometric SiC preceramic polymers. The polymer is also soluble in tetrahydrofuran and other common organic solvents. The ceramic resulting from the pyrolysis of PMSi is the closest to stoichiometric SiC that has been obtained from any polymeric precursor. The SiC ceramic film produced from PMSi is more continuous, defect-free and smoother than any reported silicon carbide film. A novel method of functionalizing metal surfaces with surface-initiated grafted polymer films is reported. This method uses 3-bromopropyltrichlorosilane to form a silane layer on the native oxide of a variety of metals, which is attached to the oxide by a degree of surface attachment. The bromopropyl group is converted to a surface-bound lithium alkyl by reaction with lithium di-t-butylbiphenyl (LiDBB), generating a surface-bound site for anionic initiation of polymerization. Polymer films of poly(methylmethacrylate) have been generated on copper, nickel, tungsten, brass, steel, titanium, and aluminum metal surfaces. These films range from 1-2 microns thickness and are robust and adhere well to the substrate surface. A degree of surface attachment of the polymer layer is seen through its robust adhesion to the substrate. Alternatively, polymer films of polyethylene and poly(methylmethacrylate) were generated on silicon and copper wafers using an organometallic initiator.
Joray, Scott James, "Surface functionalization: From polymers to ceramics" (2002). Doctoral Dissertations Available from Proquest. AAI3056245.