Supercritical carbon dioxide (scCO(2)) annealing enhances the hydrophobicity of the surfaces of asymmetric perfluorinated block copolymers. X-ray photoelectron spectroscopy (XPS) and contact angle measurement reveal that the surface domains of the fluorinated block (PF) of poly [styrene-block-4-(perfluorooctylpropyloxy)styrene] (PS-PF) become thicker than those annealed in a vacuum. Consequently, the contact angles of water on the surfaces of PS-PF block copolymers significantly increase after the scCO(2) annealing compared to those annealed in a vacuum. The surface hydrophobicity enhanced by the scCO(2) annealing is related to the thickness of the surface PF domain and the conformation of the PF block.