Synthesis of novel siloxane-containing block and graft copolymers by anionic polymerization and the macromonomer technique
The synthesis of novel well defined graft copolymers is now possible with the recent advent of the macromonomer technique. Copolymers with narrow molecular weight distributions of the backbone as well as the grafts are possible.
The anionic alkyl- lithium initiated ring opening polymerization of the hexamethylcyclotrisiloxane has been investigated to prepare polymers of controlled molecular weights and narrow molecular weight distributions. This technique was extended to the preparation of macromonomers and from these macromonomers the synthesis of graft copolymers.
These siloxane macromonomers were then incorporated into acrylic and styrenic copolymers via free radical and anionic techniques. A series of graft copolymers were characterized by a variety of methods. The resulting copolymers exhibit interesting thermal properties dependent on graft molecular weight and composition. Well-defined morphologies were observed by TEM analysis, indicative of the unique structures prepared.
Graft copolymers offer unique possibilities of structure property relationships, often forming two phase morphologies that give rise to properties of both constituents. This allows the preparation of polymers designed to give optimal characteristics.