Phase behavior and wall formation in Zr(SO4)2/CTABr and TiOSO4/CTABr mesophases

The phase behavior of Zr(SO4)(2)/CTAB composite mesophases was investigated as a function of surfactant chain length, temperature, and salt concentration by XRD. It was shown that the initial step is a rapid formation of either a pure lamellar, hexagonal, or a mixed hexagonal/lamellar phase with a low degree of condensation (room temperature), depending on the chain length of the surfactant as well as on the ionic strength of the solution. The observed features may be qualitatively explained by expected variations in the packing parameter. TiOSO4/CTAB composite mesophases were shown to form in a similar manner as Zr(SO4)(2)/CTAB, A model accounting for changes in the inorganic framework with increasing degree of intraaggregate condensation was developed. Furthermore, using a tubular reactor setup connected to an in situ XRD cell it was shown that the mesophase formation occurred immediately (<300 ms) after mixing of the reagents, which is the fastest ever recorded composite mesophase formation.