Photopolymerized acrylate copolymer films with surfaces enriched in sulfurpentafluoride (-SF5) chemistry

Acrylate monomers bearing side chains terminated in sulfur pentafluoride (- SF5) groups have been synthesized. These monomers have been copolymerized i nto films with the conventional aliphatic acrylic monomer 2-hydroxyethyl me thacrylate (HEMA) using neat cast mixed monomer films and photoinitiation. Depth-dependent surface analysis of these photocured films using X-ray phot oelectron spectroscopy shows that surfaces are enriched nonstoichiometrical ly in the -SF5 functionality, even when compositions of the binary mixed fi lm heavily favor the HEMA component. All polymer films containing the SF5-a crylate have a surface composition corresponding to an enriched overlayer o f pure SF5-acrylate. The thickness of the surface-enriched overlayer decrea ses as the bulk concentration of SF5-acrylate monomer decreases. At the low est bulk concentration examined, 1 wt % SF5-acrylate monomer, the overlayer thickness was approximately 20 Angstrom. Results mirror previous surface e nrichment observed for fluorinated/aliphatic epoxide monomer mixed films pr epared using an analogous strategy. (Schnurer, A. U.; et al. Chem, Mater. 1 996, 8, 1475-1481), This suggests that such a route to inexpensive, high-pe rformance perfluorinated coatings using small amounts of perfluorinated mon omers might be generalized to many other classes of monomers.