Mechanism of ultraviolet bonding of perfluoropolyethers revisited.

The mechanism of ultraviolet (UV) bonding of perfluoropolyether (PFPE) boundary lubricants on magnetic disk surfaces is re-examined experimentally. It is found that UV-emitted photoelectrons may contribute a negligible part, and instead the UV bonding correlates with the direct photodissociation of PFPE molecules. The UV-induced photodissociation is demonstrated to occur almost randomly on the PFPE molecular chain. The contribution from photooxidation is eliminated under nitrogen purge.