Bonded Phases - OligomericType Bonded Phases 2
It is clear, that that by alternately treating the bonded phase with water and a dichlorsilane, a series of methyoctyl silyl residues can be attached to each other that builds up the oligomeric reverse phase. The synthesis is complex and, consequently, the fluidized bed technique (which lends itself to multistage syntheses) has been used in an attempt to produce oligomeric phases.
When the last oligomeric synthesis has been completed and the final oligomer attached, the remaining silanol groups are capped with trimethyl chlorsilane or hexamethyltrisilazane. This reaction terminates the oligomeric chain with a trimethyl silyl group. The oligomeric phases are the more difficult and time consuming to make and may necessitate the use of rather complicated apparatus. As a consequence, oligomeric phases are not yet generally commercially available. It will be seen, however, that they do appear to show some advantages over the brush or bulk phases.