Controlled/living radical polymerization of vinylcyclicsilazane by RAFT process and their block copolymers

High molecular weight poly(vinyl)silazane were synthesized successfully by reversible addition fragmentation chain transfer (RAFT) polymerization in toluene at 120 degrees C, using dithiocarbamate derivatives and 2,2'-azobis-isobutyrylnitrile (AIBN) as the RAFT agents and thermal initiator, respectively. The polymerization of a vinyl-cyclicsilazane oligomer with 82.5% conversion was readily controlled to increase the molecular weight from 1000 to 12,000 g/mol with a narrow polydispersity <1.5. The resulting polymer showed a high ceramic yield of 70 wt % at 1000 degrees C. Moreover, the approach was extended successfully to the synthesis of poly(vinyl)silazane-block-polystyrene as an inorganic-organic diblock copolymer. (C) 2008 Wiley Periodicals, Inc.