2ND-GENERATION POLYMERIC PRECURSORS FOR BN AND SINCB CERAMIC MATERIALS

Our recent work directed at the design, synthesis, characterization an d applications of new types of polyborazylene and polyborosilazane pol ymers is reviewed with a focus on the use of these polymers as process able precursors to BN and SiNCB composites. A design strategy based on the controlled functionalization of preformed polymers with pendant g roups of suitable compositions and crosslinking properties has been em ployed to yield second-generation dipentylamine-polyborazylene (DPA) a nd pinacolborane-hydridopolysilazane (PIN-HPZ) polymers, which, unlike the parent polyborazylene (PB) and the borazine-hydridopolysilazane ( B-HPZ) polymers, are stable as melts and can be easily melt-spun into polymer fibers. Subsequent pyrolyses of these polymer fibers then prov ide excellent routes to BN and SiNCB ceramic fibers. (C) 1998 John Wil ey & Sons, Ltd.