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

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 (ϕPTFEMA) at the range of 0.03 ≤ ϕPTFEMA ≤ 0.60 by utilizing ATRP technique. Static contact angle tests demonstrate that the triblock copolymer with ϕPTFEMA 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/m2 for PU homopolymer while the value for triblock copolymer with ϕPTFEMA = 0.16 attained a similar value (25 mJ/m2) to that of homo PTFEMA (24 mJ/m2). This reveals that the surface is mostly covered with fluorinated segments when ϕPTFEMA ≥ 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. [Display omitted] •Synthesis of triblock copolymer-type polyurethanes with fluorinated end blocks via ATRP.•Systematic tuning of volume fraction of fluorinated end blocks in the triblock copolymers.•Investigation of self-assembly states by SAXS.•Investigation of surface properties by contact angle tests and XPS.•Correlation between surface property change and self-assembly nature of copolymers.