Preparation Principle of Super-Hydrophobic Surfaces by Phase Separation

The Flory–Huggins theory of polymer solutions combined with an evaporation process was employed to interpret the preparation mechanism of a super-hydrophobic surface by phase separation. The ternary phase diagram of a polymer/solvent/nonsolvent was calculated by using the solubility parameters of the components in the system. It indicated that with the increase of the nonsolvent fraction, the initial volume fraction of the polymer or the evaporation rate of the solvent, the evaporation time for phase separation would shorten and the phase separation rate would speed up. The polymer volume fraction in the dense phase would increase and the precipitating particles tended to collide and aggregate, resulting in a rough, super-hydrophobic surface. Experimental results were in agreement with this principle of phase separation for preparing super-hydrophobic surfaces. Membranes of acrylic resin and fluorinated acrylic resin with rough surfaces were successfully obtained by the phase separation method. Especially, the water contact angle of the fluorine-containing acrylic resin with the rough surface was greater than 150°, which satisfied the requirement of super-hydrophobicity.