Radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)

Fluoropolymers such as poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether), PFA, are chemically resistant and thermally stable materials. They have therefore found numerous applications where these are necessary material properties, for example as surface coatings for use in aerospace, in the manufacture of inert filtration membranes and as ion-conducting separators for fuel cells. A fluoropolymer has also been recently patented as a high temperature matrix resin for solid phase organic chemistry, SPOC. Because of their inherent inertness, for applications such as ion-conducting separators and SPOC resins, the fluoropolymers are first grafted with styrene that is then further modified to allow ion conduction or molecular linking, respectively. Radiation induced grafting of styrene is a most attractive approach to graft of polystyrene onto these chemically resistant substrate fluoropolymers. In the paper the radiation-induced in situ grafting of polystyrene onto PFA will be discussed. Among the fluoropolymers, PFA offers the advantage that it is melt processable and it is not as crystalline as poly(tetrafluoroethylene), PTFE. However, PFA has very similar properties to those of PTFE as it contains approximately 98 percent TFE. The role of the solvent for the styrene, the effect of the radiation dose rate and total radiation dose will also be elucidated through measurements of the grafting yields and through Raman microprobe mapping of grafted surfaces and delineation of the depth profile for the polystyrene graft. The results of the study will be interpreted in terms of the potential applications for the grafted polymers as ion-conducting membranes and as matrix resins for SPOC