A very broad variation of functionality of bonded species could be attached to the silica surface. The most popular is an organofunctional groups, R. R may carry substituents of various functionality such as alcoholic or phenolic hydroxyl, amine, phenyl, carbonyl, nitril etc.
The functional group R can be linked to the surface silicon atoms in the following ways:
Reaction of monochlorosilane with hydroxilated silica surface leads to the attachment of only one alkylsilane ligand to one silanol group. The type of bonded layer which involves the formation of a monomolecular organic layer on the silica surface is called "monomeric bonding".
Polymeric phases can be prepared by reacting silica with di- or trichlorosilane in the presence of trace amount of water, which leads to the formation of tree-like structure on one reacted silanol group of silica surface.
Schematic of monomeric and polymeric bonded layers