Graft Polymerization Induced by Atmospheric Pressure Plasma

Case 2006-661

BACKGROUND

Polymer thin films have been used for surface engineering of inorganic and organic substrate surfaces to enhance substrate chemical selectivity and modify surface topology in such areas as biotechnology, tribology, chromatography, chemical sensors and separation technology. Thin polymer films which are applied via traditional spin-coating or surface adsorption have low thermal and chemical stability which can lead to film dewetting and surface degradation.Covalently bonded polymer films can be formed by graft polymerizing a suitable monomer onto substrate surfaces via the use of free-radical initiators, cationic/anionic initiators, or by using a combination of a catalyst and initiators for controlled graft polymerization. Yet each of these techniques relies on the presence of initiator sites which must be first covalently grafted to the surface by techniques such as silylation, self assembly, or functionalized molecules that act as anchoring sites for monomer grafting. It is noted that in the case of inorganic oxide surfaces, the surface density of initiation sites is limited by the intrinsic availability of native surface hydroxyl groups which typically serve for attaching the active anchoring species to the substrate. Alternative methods of graft polymerization that are based on surface activation via low pressure plasma surface activation have also been developed. However, such approaches are expensive, impractical for large-scale applications and are also difficult to control.

INNOVATION

UCLA researchers have developed a novel process for surface modification of a broad range of inorganic surfaces via atmospheric plasma-induced graft polymerization. The process utilizes atmospheric gas plasma for surface activation with subsequent graft polymerization of the desired vinyl monomers. The presence of the grafted polymer chains on the substrate was confirmed by infrared spectroscopy. Additionally, surface topology and surface feature uniformity was evaluated by Atomic Force Microscopy (AFM).

APPLICATIONS

• Membrane surface structuring for various separation tasks
• Sorption resins
• Chemical sensors
• Adhesion enhancement
• Lubrication
• Water repulsion
• Non-stick, staining surfaces
• Conductive Nanomaterials

ADVANTAGES

• The current approach demonstrates that direct surface activation by atmospheric plasma is possible.
• Inorganic oxide surfaces can be directly treated via this method.
• Surface density of grafted polymer chains can be controlled.
• UV irradiation is not required.
• The limitations of low pressure plasma surface activation are avoided.