We have prepared self-supporting, free-standing titania-surfactant mesostructured films via spontaneous growth on the surface of ethanolic solutions, as an alternative synthetic route to evaporation induced self-assembly. The initial stages of surfactant templating and interfacial film formation in alcoholic solutions of titania with a polyethylene-poly(ethylene glycol) surfactant have been observed by small angle neutron scattering and Brewster angle microscopy. Variation of parameters including the titania precursor concentration, acid concentration, and surfactant concentration allowed formation times and pathways to be probed. These time-resolved observations of titania development represent a novel achievement in formation studies and have allowed a formation mechanism for titania-surfactant films to be proposed. Micelles in solution undergo an initial slow accumulation of titania, followed by rapid growth of a titania shell, followed again by a slow growth period, and these species accumulate at the solution interface to form the film via a phase transition driven by evaporation from the solution surface. This mechanism shows no solution aggregation in early developmental stages and is significant in understanding early solution phase development and for developing new materials based on evaporation induced self-assembly processes as well as for spontaneous growth of films at interfaces.
Edler, K. J., Hawley, A. M., O'Driscoll, B. M. D., & Schweins, R. (2010). Association of titania with nonionic block copolymers in ethanol: the early stages of templating and film formation. Chemistry of Materials, 22(16), 4579-4590. https://doi.org/10.1021/cm100511z