Macromolecules, Vol.31, No.22, 7845-7850, 1998
Reversible surface properties of glass plate and capillary tube grafted by photopolymerization of N-isopropylacrylamide
A new, simple, and effective method to modify the surface of glass plate and quartz capillary tube by ultraviolet (UV) photopolymerization of N-isopropylacrylamide (NIPAAm) has been developed. A photosensitizer, silane coupling agent with the dithiocarbamate group, was synthesized by the condensation re action between chloropropyltrimethoxysilane and sodium N,N'-diethyldithiocarbamate. The thiocarbamate groups were installed on the glass surface by coupling the silane agent with the hydroxyl groups on the glass surface. Subsequently, the silane-modified surface was photografted by NIPAAm in the presence of N,N-methylenebisacrylamide. The characteristics of the glass surfaces were examined by scanning electronic microscopy (SEM) and the static and dynamic contact angle techniques. The thickness of grafted PNIPAAm film is less than 320 nm, and the surface showed a completely hydrophilic nature at about room temperature and a hydrophobic nature above 40 degrees C. The water meniscus height in a capillary tube (2 mm in diameter), whose wall was coated with a cross-linked NIPAAm layer, was rose to 7 mm by changing the temperature of the water in contact with a capillary tube by about 20 degrees C. The rapid and remarkable change in surface properties with the temperature change makes it applicable as actuators, modulators, and the antifouling surface and microchannel of separation membranes.