MECHANISM OF ULTRAVIOLET AND ELECTRON BONDING OF PERFLUOROPOLYETHERS

It has recently been reported that thin films of perfluoropolyethers (PFPE's) can be bonded to a variety of substrates under illumination of 185-nm ultraviolet (UV) light. In this paper we examine the bonding of thin perfluoropolyether films by low-energy electrons and UV light. It is shown that the bonding takes place through interaction of the perfluoropolyether molecule, with a low-energy photoelectron created by excitation of the substrate by the UV photons. The perfluoropolyether molecule subsequently undergoes a dissociative electron attachment, resulting in the formation of a radical and a F- ion. It is likely that radical propagation and termination steps then cross-link the polymer and attach it to the substrate. The similarities and differences between electron-bonded and UV-bonded perfluoropolyether films are discussed.