Nanocomposites via Polymerization from Silica

Abstract

This chapter shows how the previously synthesized special RAFT agents can be immobilized on the surface of different types of silica substrates via methoxysilyl moieties located at the end of their stabilizing Z-groups. In subsequent surface-confined RAFT polymerizations, which give rise to particular polymer–silica nanocomposites according to a grafting-from approach, these adaptively designed RAFT agents can play to their special strengths: The doubly anchored RAFT agent leads to polymer loops on the surface of fumed silica through a polymerization mechanism in which the propagating radicals as well as the mediating groups remain attached to the surface. By the use of a RAFT agent with an anchor group only capable of forming a single covalent bond (rather than three as for a conventional RAFT agent in a control experiment), the crosslinking of colloidally dispersed carrier particles of silica during the immobilization process can successfully be prevented.