Surface photografting of polymer films and fibers for adhesion and adsorption control

摘要

Since the invention of an efficient one-step 'surface photografting' in our laboratories and its development as a batch process and a continuous process 10 years ago, the method has been applied extensively for adhesion and adsorption control of commercial film and fiber samples. In the batch process, the substrate is irradiated with UV light in an atmosphere of photoinitiator and monomer vapor in an inert gas. In the continuous process, the substrate is presoaked in a solution of photoinitiator and monomer which forms a thin liquid layer. The substrate is then UV-irradiated on line. In both processes, radicals are formed on the substrate surface by hydrogen abstraction. The surface radicals add monomer and form grafted chains as a thin surface layer which is analyzed by ESCA and reflection IR spectroscopy and by microtitration. A grafted layer 2 to 8 nm thick of a functional monomer, e.g. acrylic acid, acrylamide, vinyl pyridine or glycidyl acrylate, on an inert polymer surface, e.g. of a polyolefin or linear polyester, decreases the contact angle of water to complete wetting, increases the adsorption of textile dyes as much as 15 times and the adhesion to epoxy resin 3 to 6 times. Grafting with epoxyacrylates enhances surface bonding of heparin and polypeptides to the substrate. Secondary reaction of the epoxy groups with poly(ethylene glycol) makes the polymer surface hydrophilic, which prevents thrombosis of proteins.