Preparation of mesoporous titania thin films with well-crystallized frameworks by using thermally stable triblock copolymers

Mesoporous titania (TiO2) thin films are prepared by a spin-coating method using new laboratory-made polystyrene-block-polybutadiene-block-polystyrene-based triblock copolymers in which the polystyrene block is functionalized with hydrophilic sulfonic groups (abbreviated as sulfonated HmSEBmS). The polymer used in this study is more thermally stable than commercial Pluronic-type block copolymers (e.g. P123 and F127). As-prepared TiO2 thin films are calcined under various temperatures. The calcined films are systematically characterized by low-angle and wide-angle XRD, scanning electron microscopy (SEM), and nitrogen gas adsorptiondesorption isotherms. As calcination temperatures increase, crystal growth proceeds in the pore walls and the phase transformation from anatase to rutile occurs. Even after calcination at 550 and 600 degrees C, the thin films nicely preserve high surface areas. On the other hand, the surface areas of mesoporous TiO2 prepared from P123 are markedly decreased after calcination at 550 degrees C.