Superhydrophobic fluorinated polyurethane films

A superhydrophobic polyurethane-based film is described, on which the water advancing and recedingcontact angles are 150° and 82°, respectively. The film was prepared from surface-fluorinatedpolyurethane (PU), obtained from a well-defined fluorinated isocyanate, with silica particles incorporatedwithin the film. In the absence of the silica particles, smooth fluorinated PU films with about 2 wt% fluorinedemonstrate water advancing and receding contact angles of 110° and 63°, respectively. A majorcause for the large contact angle hysteresis, similar to the so-called ‘sticky’ superhydrophobic behavior,on the roughened PU films is believed to originate from the surface reorganization of the fluorinatedPU upon contact with water, which is characteristic for the partially fluorinated PU film. When a similarpoly(dimethylsiloxane) (PDMS)-based roughened film was made, the water contact angle hysteresis couldbe reduced significantly, since the long PDMS chain can effectively suppress the surface reorganizationupon contact with water.