Bicontinuous cubic mesoporous materials with biphasic structures

The replication of amphiphilic systems within an inorganic silica matrix allows the study of the fundamental properties of mesostructural changes, that is, kinetic and structural parameters. Herein we report a detailed study of the transition between cubic bicontinuous mesostructure with space groups Ia3̄d and Pn3̄m symmetry, which are associated with the minimal G and D surfaces, respectively. The transition may be induced through micellar swelling of the anionic amphiphilic surfactant N-lauroyl alanine by trimethylbenzene. Rich kinetic behaviour is observed and has been exploited to prepare particles with biphasic structures. Transmission electron microscopy evidence indicates that there is epitaxial growth from one mesostructure to the other involving the [111] and [110] orientations of the Ia3̄d and Pn3̄m symmetry structures, respectively. From kinetic studies, we show that the formation of the Ia3̄d mesophase is preceded by a hexagonal phase (plane group p6mm) and an epitaxial relationship has been observed involving the sixfold or 3̄ axis orientations of both structures. Our data suggests that the Pn3̄m mesostructure is kinetically stable at low temperatures whereas the Ia3̄d mesostructure is the more stable structure after prolonged periods of hydrothermal treatment. We present evidence from transmission electron microscopy and small-angle X-ray diffractograms and also electron crystallography modelling of the unit cells at particular points in the structural change. Expect the unexpected! The unexpected happens at the interface. Mesoporous particles with biphasic cubic bicontinuous structures have been prepared through micellar swelling and studied by using electron crystallography and imaging (see figure).