Structural manipulation of colloidal silica.

Structural properties of the nanosized silica Ludox TMA with novel functionalizations have been investigated. Silica is stabilized in aqueous solution at a pH value higher than the pK(a) of silicic acid. A surface modification consisting of poly(p-benzamide)s functionalized with derivatized nucleobases on the C-terminus and cationic pyridinium functions on the N-terminus of the polymer chain was carried out. Due to the negatively charged surface, strong physisorption of the cationic pyridinium functions occurs. It is possible to stabilize diluted solutions of silica without agglomeration in solvents with various polarities by using pyridinium cations. Defined structures could be created according to the hydrogen donor/acceptor potential of the introduced nucleobase. Surprisingly the interactions between the same nucleobases are already sufficient for strong particle-particle interactions. Dramatic effects on the structural behavior are characterized by PCS, (S)TEM and EFTEM.