Nonaqueous Synthesis of Mesostructured Aluminophosphate/Surfactant Composites:  Synthesis, Characterization, and In-Situ SAXS Studies

Mesostructured aluminophosphate/dodecyl phosphate composite materials were synthesized under aqueous and alcoholic conditions. The syntheses were monitored by temperature- and time-resolved in-situ small-angle X-ray scattering (SAXS). In the aqueous synthesis, a lamellar mesostructure is formed within the first few minutes of the reaction; this structure maintains a constant d spacing independent of the reaction time and temperature. The alcoholic synthesis at low temperature yields a mixture of a lamellar and a supposedly inverted hexagonal mesostructure. SAXS investigations show that these two phases evolve competitively. The lamellar structure is favored by higher temperatures and/or longer synthesis times; above ∼70 °C it is formed exclusively. Mixtures of both phases can be isolated as solid materials, but thermal analysis shows that the inverted hexagonal product transforms into the lamellar phase at ∼35−43 °C. The alcoholic synthesis is a highly cooperative reaction; the pure surfactant/alcohol systems are not lyotropic as long as the inorganic reactants are absent. In comparison, the surfactant/water system with the same surfactant concentrations as employed for the aqueous syntheses is lyotropic with a lamellar structure.