Matthias Ide

Developing a new and versatile ordered mesoporous organosilica as a pH and temperature stable chromatographic packing material

Periodic Mesoporous Organosilicas (PMOs) have been successfully spray dried for the first time using a novel cyclic multifunctional organosilane molecule. By reducing the siloxane bridge formation both in the polymerisation and in the anchoring of the side groups an organic/inorganic hybrid material was designed, depicting inherently improved chemical stability and much increased organic content. The spherical silica particles were applied as a hydrolytically stable stationary phase in reversed phase HPLC. They proved to be both highly retentive and stable in a pH range from 1.75 to 12 and up to 150 °C in 60 v% water. Both the backbone and the functionalities of the material exhibit this high stability.

Isomeric periodic mesoporous organosilicas with controllable properties

The synthesis procedure for isomeric periodic mesoporous organosilicas with E-configured ethenylene bridges was investigated using the homemade pure E-isomer of 1,2-bis(triethoxysilyl)ethene. The pH, aging temperature and the presence of cosolvents played a key role in obtaining well-ordered mesoporous materials with controllable properties and morphologies. By fine-tuning the reaction mixture acidity, PMOs with high surface areas and pore volumes could be attained. By selecting various alcohols as cosolvents and optimizing the alcohol concentration, PMOs with crystal-like disc shaped, fibrous and spherical particle morphologies were obtained. The synthesis temperature of these ethenylene-bridged PMOs influences the pore size, structure, connectivity and volume.

Calcium phosphate cements modified with pore expanded SBA-15 materials

The effects of adding a mesoporous ordered silica to a calcium phosphate cement (CPC) based on α-tricalcium phosphate (α-TCP) are described in this study. The influence of this mesoporous seed material and of the phosphate concentrations in the cement liquid on the physico-chemical, mechanical and microstructural properties of the CPC was investigated. SBA-15 and ultra-large pore (ULP) SBA-15 were used as seed materials. For the latter, a novel reproducible synthesis procedure was developed. When using a 4 wt% Na2HPO4 solution, the α-TCP based cement exhibited setting times convenient for clinical applications, but the material was very weak and no conversion to a calcium-deficient hydroxyapatite (CDHAp) occurred. Adding either SBA-15 or ULP SBA-15 to the CPC stimulated the nucleation and growth of apatite crystals and influenced the microstructure of the set cement. The ratio between the concentration of silica in the cement powder and the phosphate concentration in the cement liquid was crucial for tailoring the properties of the CPC. Cements with 5 wt% ULP SBA-15 as seed material could be used in a clinical setting for load-bearing applications.