A facile method for the preferential alignment of mesochannels in silica films by solution flow

We report a simple and one-step processing method to prepare mesoporous silica films with preferential alignment of cylindrical mesochannels during the condensation of TEOS in the presence of Pluronic P123 (EO20PO70EO20, Mw = 5800) triblock copolymer, employed as a structure-directing agent. The alignment of mesochannels in a mesoporous silica film is achieved by the directional solution flow without additional complex treatments on the substrate. It is shown that the hexagonal arrays of cylindrical mesopores are oriented parallel to the direction of solution flow when the film is thin enough (∼200 nm). Above the critical film thickness, the effect of the directional solution flow is not significant enough such that the orientation near the substrate does not propagate across the entire film, yielding the mixed orientation of mesochannels. In-plane and out-of-plane XRD measurements along with FE-SEM measurements were used to characterize the degree of alignment of mesochannels.