Phase behavior and preparation of mesoporous silica in aqueous mixtures of fluorinated surfactant and hydrophobic fluorinated polymer

Abstract

The phase behavior and formation of self-assemblies in the ternary water/fluorinated surfactant (C 8F 17EO 10)/hydrophobic fluorinated polymer (C 3F 6O) n COOH system and the application of those assemblies in the preparation of mesostructured silica have been investigated by means of phase study, small angle X-ray scattering, and rheology. Hexagonal (H 1), bicontinuous cubic (V 1) with Ia3d symmetry, and polymer rich lamellar ( L α ′ ) are observed in the ternary diagram. C 8F 17EO 10 molecules are dissolved in polymer rich aggregates, whereas (C 3F 6O) n COOH molecules are practically insoluble in the surfactant lamellar phase due to packing restrictions. Hence, two types of lamellar phases exist: one with surfactant rich ( L α ) and the other with polymer rich ( L α ′ ) in the water/C 8F 17EO 10/(C 3F 6O) n COOH system. As suggested by rheological measurements, worm-like micelles are present in C 8F 17EO 10 aqueous solutions but a rod-sphere transition takes place by solubilization of (C 3F 6O) n COOH. C 8F 17EO 10 acts as a structure directing agent for the preparation of hexagonal mesoporous silica by the precipitation method. The addition of (C 3F 6O) n COOH induces the formation of larger but disordered pores.