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.