The effect of direct fluorination of polydimethylsiloxane films on their surface properties.

To investigate the effect of fluorination on the surface of polydimethylsiloxane (PDMS) film, direct fluorination was performed under a mild condition (approx. 2000 micromol/mol F(2) in nitrogen) for 120 min. No structural damage of PDMS films was observed on the scanning electron microscopic images under the condition. Fourier-transform infrared/attenuated total reflectance (FTIR/ATR) and energy dispersive X-ray spectroscopy (EDS) results showed a successful fluorine introduction resulting in the structural change of PDMS. Surface property changes of PDMS films with respect to the extent of direct fluorination were also examined. Contact angles of water and alcohols on the PDMS surfaces decreased as fluorination time increased. Most alcohols showed greater decrease than water in the contact angle as a result of long-term fluorination, which sometimes results in zero contact angles of alcohols on the PDMS surfaces. Surface energy of PDMS films increased more than 200% after the direct fluorination for 120 min.