CATIONIC RING-OPENING POLYMERIZATION OF CYCLOSILOXANES INITIATED BY ELECTRON-DEFICIENT ORGANOSILICON REAGENTS

The cationic ring-opening polymerization of octamethylcyclotetrasiloxa ne initiated by R(3)SiH-Ph(3)C(+)B(C6F5)(4)(-) (trityl TPFPB) in the a bsence of protic acids has been investigated. Mechanistic studies demo nstrate that the polymerization proceeds by a single ''long-lived'' ox onium ion end. This novel polymerization is distinct from those initia ted by protic acids. Cyclotrisiloxanes containing vinyl or trifluoropr opyl groups could be polymerized in a similar manner, while the homopo lymerization of trimethyltriphenylcyclotrisiloxane failed. The method has also been extended to the preparation of siloxane-containing diblo ck copolymers and comblike branched polysiloxanes.