Hydrophilic surface formation on polymers and its applications

A new surface modification technique, so-called ion assisted reaction (IAR) has been developed at the Korea Institute of Science and Technology (KIST) Ion Beam Laboratory while modifying the surface of polymer results in many of industrial applications. The IAR, in which a keV ion beam is irradiated on the surface of polymer in reactive gases environment, has been developed for improving wettability of polymer surface and enhancing adhesion of other materials. The contact angles of water drops with modified polymers were significantly reduced by Ar+ ion irradiation with flowing oxygen gas environment than without flowing oxygen gas. Change of contact angles for the modified polymers was explained by a two-step chemical reaction among polymer matrix, energetic ions and oxygen gas. X-ray photoelectron analysis showed that hydrophilic groups were formed on the surface of polymers by chemical reaction between the unstable chains induced by ion irradiation and the oxygen gas, and the hydrophilic groups were identified as –(C–O)–, –(CO)– and –(CO)–O– bonds. The enhanced adhesion between metal and modified polymers was explained by the formation of charge transfer complex in polymer and electron donors in metal. Possible industrial applications of the IAR are to be discussed.