| Popis: |
We report the synthesis of alkaline earth induced/containing complex constructions of mesoscale mesoporous silica particles with novel patterned surfaces and controllable porosity and morphology by employing a poly(acrylic acid) -cetyltrimethylammonium bromide complex template. The addition of the alkaline earth metals Mg or Sr induced the morphosynthesis of some fascinating curved particles exhibiting complex discoid and gyroid morphologies with novel patterned surfaces of increased complexity consisting of platelike fins or regular creased coronas. The use of Ca results in ordinary particles without long-range morphology. The uncalcined materials possess long-range hexagonal ordering, while upon calcination the respective loss of order does not affect the particular morphology. The materials are synthesized and preserve their intrinsic characteristics in a wide range of pH values extending from 5.5 to 9.0. The morphology, the porosity, and the metal concentration of the particles are affected and can be controlled by the pH. Increase of the latter favors the transformation from discoid with peripheral platelike fins to gyroid particles with creased, thick coronas in the case of Sr, while for the case of Mg at pH 9.0 the gyroids embody either discoids with peripheral platelike fins or patterned coronas. At the lower pH the materials are microporous. When the pH is increased, mesoporous materials are obtained. In this way porosity is controlled by a simple variation of pH, without the use of surfactants with longer chains. The amount of metal on the mesostructure is also increased with the pH. Chemistry of Materials |
