Photopolymerized Acrylate Copolymer Films with Surfaces Enriched in Sulfur Pentafluoride (−SF5) Chemistry

Acrylate monomers bearing side chains terminated in sulfur pentafluoride (−SF 5 ) groups have been synthesized. These monomers have been copolymerized into films with the conventional aliphatic acrylic monomer 2-hydroxyethyl methacrylate (HEMA) using neat cast mixed monomer films and photoinitiation. Depth-dependent surface analysis of these photocured films using X-ray photoelectron spectroscopy shows that surfaces are enriched nonstoichiometrically in the −SF 5 functionality, even when compositions of the binary mixed film heavily favor the HEMA component. All polymer films containing the SF 5 −acrylate have a surface composition corresponding to an enriched overlayer of pure SF 5 −acrylate. The thickness of the surface-enriched overlayer decreases as the bulk concentration of SF 5 −acrylate monomer decreases. At the lowest bulk concentration examined, 1 wt % SF 5 −acrylate monomer, the overlayer thickness was approximately 20 Å. Results mirror previous surface enrichment observed for fluorinated/aliphatic epoxide monomer mixed films prepared using an analogous strategy. (Schnurer, A. U.; et al. Chem. Mater. 1996, 8, 1475−1481). This suggests that such a route to inexpensive, high-performance perfluorinated coatings using small amounts of perfluorinated monomers might be generalized to many other classes of monomers.