The outermost atomic layer of thin films of fluorinated polymethacrylates

The surface properties of a series of copolymers of perfluoroalkyl methacrylates (CH2=C(CH3)COOCH2CnF2n+1, n = 1, 6, or 10) and Me methacrylate (MMA) and of blends of perfluorooctyl-end-capped poly(Me methacrylate) (PMMA) and pure PMMA were studied. The introduction of perfluoroalkyl groups significantly lowers the surface energy of fluoropolymers as detd. by the acid-base approach. The XPS data confirm a higher fluorine concn. in the surface region (the outer 3.8 nm) as compared to the bulk. The fluorine d. in the outermost at. layer is quant. detd. by low-energy ion scattering (LEIS). A linear relation is found between the fluorine d. in the outermost at. layer and the surface energy of the partially fluorinated polymethacrylates, irresp. of the length of the perfluoroalkyl chain. This linearity confirms Langmuir's principle of independent surface action. Deviation from this linear relation exists for both highly and sparsely fluorinated polymethacrylates and can be ascribed to the local (surface) ordering of the fluorinated tails and MMA units, resp. The study contributes to understanding the correlations between macroscopic surface properties and microscopic surface chem. compn. [on SciFinder (R)]