Hydrophobicity enhancement of polyurethanes by attaching fluorinated end blocks via ATRP and correlation between surface properties and self-assembly nature

Abstract Hydrophobicity enhancement for polyurethane (PU) materials is important to explore new application range of PUs. We here prepare the triblock copolymer series with a PU middle block and fluorinated end blocks, poly (2,2,2-trifluoroethyl methacrylate) (PTFEMA), with various PTFEMA volume fraction ( ϕ PTFEMA ) at the range of 0.03 ≤  ϕ PTFEMA  ≤ 0.60 by utilizing ATRP technique. Static contact angle tests demonstrate that the triblock copolymer with ϕ PTFEMA of 0.03 already attained much higher value of water contact angle (∼95°) than the value (∼74°) of PU homopolymer. The surface free energy ( γ ) estimated by Owens-Wendt method was 48 mJ/m 2 for PU homopolymer while the value for triblock copolymer with ϕ PTFEMA  = 0.16 attained a similar value (25 mJ/m 2 ) to that of homo PTFEMA (24 mJ/m 2 ). This reveals that the surface is mostly covered with fluorinated segments when ϕ PTFEMA  ≥ 0.16, which is supported by XPS analysis. We found from SAXS data that these surface property changes were fully correlated with the changes of self-assembly nature of copolymers depending on the length of PTFEMA end blocks.