Free-standing and oriented mesoporous silica films grown at the air-water interface

SURFACTANT assemblies can function as templates for the deposition of silicates to form mesoporous silicas¹. Recently we described a surfactant-templated synthesis of oriented mesoporous silica films grown at the mica-water interface². Here we show that such films can be grown without a solid substrate, by surfactant templating at the interface between air and water. The films are continuous and have a root-mean-square surface roughness of about 3 A. They are resilient enough to withstand significant bending, and are sufficiently flexible to be transferred onto substrates of different shapes. We propose a model for film formation which ascribes a dual-templating role to the surfactant: we suggest that both a surfactant overstructure at the air-water interface and micellar aggregates in solution interact collectively with the soluble, polymerizable silicate building blocks. These films might find applications in catalysis, separation technology and biomedicine.