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 moni tored by temperature- and time-resolved in-situ small-angle X-ray scatterin g (SAXS). In the aqueous synthesis, a lamellar mesostructure is formed with in the first few minutes of the reaction; this structure maintains a consta nt d spacing independent of the reaction time and temperature. The alcoholi c synthesis at low temperature yields a mixture of a lamellar and a suppose dly inverted hexagonal mesostructure. SAXS investigations show that these t wo phases evolve competitively. The lamellar structure is favored by higher temperatures and/or longer synthesis times; above similar to 70 degrees C it is formed exclusively. Mixtures of both phases can be isolated as solid materials, but thermal analysis shows that the inverted hexagonal product t ransforms into the lamellar phase at similar to 35-43 degrees C. The alcoho lic synthesis is a highly cooperative reaction; the pure surfactant/alcohol systems are not lyotropic as long as the inorganic reactants are absent. I n comparison, the surfactant/water system with the same surfactant concentr ations as employed for the aqueous syntheses is lyotropic with a lamellar s tructure.