This article gives an overall view of the mechanisms involved in the mesostructuring that takes place during the formation of surfactant‐templated inorganic materials by evaporation. Since such a method of preparation is well suited to fabricating thin films by dip coating, spin coating, casting, or spraying, it is of paramount interest to draw a general description of the processes occurring during the formation of self‐assembled hybrid organic/inorganic materials, taking into account all critical parameters. The following study is based on very recent works on the meso‐organization of thin silica films using tetraethylorthosilicate (TEOS) as the inorganic source and cetyltrimethylammonium bromide (CTAB) as the structuring agent, but we will show that the method can also be extended to other systems based on non‐silica oxides and block copolymer surfactants. We demonstrate that the organization depends mainly on the chemical composition of the film when it reaches the modulable steady state (MSS), where the inorganic framework is still flexible and the composition is stable after reaching an equilibrium in the diffusion of volatile species. This MSS state is generally attained seconds after the drying line, and the film's composition depends on various parameters: the relative vapor pressures in the environment, the evaporation conditions, and the chemical conditions in the initial solution. Diagrams of textures, in which the stabilized structures are controlled by local minima, are proposed to explain the complex phenomena associated with mesostructuring induced by evaporation.

Structure‐directing agents that aid in the formation of ordered, mesostructured titania have been found in poly(ethylene oxide) surfactants. Thermal treatment of the films results in stiffening of the titania network, thereby providing straight channels with elliptical pore cross sections (see Figure). The preparation, characterization, and properties of these films are thoroughly discussed, as well as the possibility of extending the technique for the preparation of 3D structures.

International audiencePorous sol−gel silica films are prepared using different PMMA latex nanoparticles, 30−80 nm in diameter, as sacrificial templates. By changing the size and the content of the latex particles in the deposited silica sol, it was possible for the first time to tailor the porosity of the sol−gel films (uniform pore size and porous fraction from 0.10 to 0.74) independently of their thickness. This is the consequence of a low microporosity in the silica walls as shown by the correspondence between the measured porous fraction after calcination and the starting latex volume fraction. No ethanol capillary condensation occurs in these films before high partial pressure (above 0.9), leading to a stable refractive index that can be tuned in a large range (from 1.15 to 1.40 at 600 nm). A porosity percolation transition with the opening of the extrinsic pore interconnection was observed at a pore fraction threshold of about 0.40 for different sizes of the initial template. Below the threshold, the films showed a closed porosity structure with a low stable refractive index (down to 1.29 at 600 nm), opening the way to their use for antireflective applications