Silica films having zigzag mesoporous structures with fixed kink angles

Mesoporous silica films with a highly controlled unique zigzag porous structure are prepared on a rubbing-treated polyimide film. The honeycomb-packed tubular pores in the films have two distinct in-plane alignment directions with respect to the rubbing direction; that is, the films have an in-plane zigzag mesoporous structure with a fixed kink angle. The kink angle is controllable by the molar ratio of tetraethoxysilane as a silica source to surfactant in the reactant solution, and the increase of the ratio results in larger kink angles. The zigzag structure is found to be formed through the formation of an initial immature mesostructured film with uniaxially aligned rodlike surfactant assemblies. It is highly probable that the observed in-plane bending of the pores is caused by the translations shift of the positions of the adsorbed surfactant molecules along the polyimide chains on the surface and that the shift is caused by the steric effects between the adjacent hydrophilic components consisting of surfactant head groups and silica oligomers. The present results show that a unique nanoscale structure, which can hardly be obtained through a reaction under homogeneous conditions, can be formed under the heterogeneous conditions in which the reaction takes place within a restricted environment.