Preparation of a mesoporous silica film with a strictly aligned porous structure through a sol-gel process

A novel strategy for the preparation of a mesoporous silica film, in which the in-plane alignment of the honeycomb packed mesochannels is strictly controlled, is developed. The highly aligned porous structure is achieved by using a substrate with a rubbing-treated polyimide coating in the evaporation induced self-assembly process. It is shown that the controlled porous structure is formed over the entire thickness of the film and that the alignment distribution is much narrower than that in the films prepared by the conventional process based on a heterogeneous nucleation and growth mechanism. In the present process, the aligned porous structure would be formed through a directional lamellar-to-hexagonal phase transition from the substrate surface toward the air/film interface. The new formation mechanism as well as the lower process temperature enables the observed strict alignment control of the mesochannels.