Deposition and growth of novel silicon oxide and ammonium salt coatings

Abstract

Modification of solid surfaces provides a cost effective route for producing novel properties, such as adhesion, permeability, wettability, etc. The aim of this work was to modify polyolefin surfaces with silicon dioxide and ammonium salt overlayers. Silicon dioxide layers were formed by oxygen plasma treatment of polydimethylsiloxane (PDMS) rich polyolefin surfaces. PDMS enrichment at the surface was achieved by preparing polymer blends containing PDMS homopolymer or copolymer and polyolefin. The surface segregation behaviour of these blends was studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements. Next, e-beam treatment of solvent-cast 3-(-2-aminoethylamino) propyltrimethoxy-silane (Z-6020 / pentaerythritol tetracrylate (PETA) / itaconic acid (ITA) mixtures onto polypropylene films was investigated. An enhancement in gas barrier was measured. This was attributed to the formation of ammonium salt, cross-linking, and siloxane networks. The findings of this work lead to the development of a novel solventless method for depositing ionically-interacting polymeric networks. This new approach comprised plasma co-polymerisation/deposition of monomers containing carboxylic, amine, and anhydride groups. The final part of this thesis describes the formation of highly fluorinated surfaces using CF4 plasma treatment of the polydimethylsiloxane / polyethylene (PDMS/PE), polydimethylsiloxane / polypropylene (PDMS/PP) blends, and pure PDMS films. The importance of plasma parameters such as the input power, duration, and of pulse duty cycle on the extent of fluorination was investigated.