Synthesis of inorganic and organic-inorganic hybrid hollow particles using a cationic surfactant with a partially fluorinated tail

A new partially fluorinated cationic surfactant, 1-(10-perfluorooctyldecyl) pyridinium bromide monohydrate, is synthesized and used as the template for mesoporous ceramic and inorganic-organic hybrid particles. Several hydrolyzed alkoxide precursors are shown to co-assemble with this surfactant to form hollow vesicle-like particles, and the effect of changing the alkoxide chemical structure on the formation of these particles is examined. Tetramethoxysilane produces cubic or columnar particles without hollow cavities, but all other tetra-n-alkoxysilanes tested up to the n-butoxide produce hollow particles. As the alkoxide length increases, the shell structure changes from multilayered (with Si(OC₂H₅)₄) to a single thin layer (with Si(OC₃H₇)₄) to a single thick layer (with Si(OC₄H₉)₄). The stability of the fluorocarbon bilayers allows similar vesicular structures to be obtained in organic-inorganic hybrids prepared with bridged alkoxysilanes. Ethylene-bridged silanes display similar structures to tetra-alkoxysilanes. However, the hollow structures appear to partially collapse when the bridging chain is too long (octylene) and no hollow particles are formed with bis(trialkoxysilylpropyl)amines.