Reversible light-induced wettability of fluorine-containing azobenzene-derived Langmuir-Blodgett films

An azobenzene derivative [4-(6-oxo-hexacarboxylic acid)-3-trifluoromethyl-a zobenzene] was synthesized and transferred onto a solid substrate by the La ngmuir-Blodgett (LB) technique. The films undergo reversible wettability ch anges upon irradiation with ultraviolet (UV, 365 +/- 10 nm) and visible (43 6 +/- 10 nm) light. This property of reversible wettability of the LB film is confirmed directly by contact angle measurement, UV-Vis absorption spect roscopy and atomic force microscopy (AFM). The results suggest that the wet tability change is due to a photoinduced surface energy change. Copyright ( C) 2001 John Wiley & Sons, Ltd.