Ultraviolet Bonding of PFPE With Carbon Overcoat: Surface Energy and Spreading

Ultraviolet (UV) irradiation effects on the functional perfluoropolyether (PFPE), i.e., Ztetraol films, were investigated by studying the bonded film thickness as well as the surface energy of PFPE lubricated media using Lifshitz-van der Waals and Lewis acid/base (LW/AB) theory. It was found that short-time UV irradiation enhanced the bonding of Ztetraol film with ion beam deposited carbon overcoat, which is attributed to the direct photodissociation of PFPE molecules. Long-time UV irradiation degraded PFPE chain and caused the loss of lubricant by evaporation. L-t plot was further employed to analyze the spreading behaviors of Ztetraol films, where L represents the distance of the leading edge of the lubricant film travels in the time t. With UV irradiation, the spreading of Ztetraol films was retarded possibly due to the enhancement of bonding of Ztetraol with overcoat and cross-linking between Ztetraol molecules.