Facile control of surface wettability in TiO2/poly(methyl methacrylate) composite films

► We present a facile method to control the water affinity of the surface by composite films. ► The contact angle of PMMA/TiO2 composite films reaches 140° at 50 vol.% of TiO2. ► Preferential orientation of PMMA accounts for the strong hydrophobicity. ► UV light exposure turns the surface of the films to be superhydrophilic. ► Polymer removal and mesoporous structure are responsible for superhydrophilicity.