PRECURSORS FOR SILICON-CARBIDE SYNTHESIZED FROM DICHLOROMETHYLSILANE DERIVATIVES

Several polysilanes, including two groups of copolymers and a group of ter-polymers, with overall functionalities ranging between 2 and 3 we re prepared using the alkali metal dechlorination reaction. The yields of the soluble solid fractions of these polymers (the potential ceram ic precursor) were in the range 40-70% wt and decreased with increasin g overall functionalities in both cases of co- and terpolymers. The mo lecular weights and FT-IR spectra of the precursors have been determin ed and the ceramic in the residue after pyrolysis has been identified as silicon carbide. The pyrolytic yield can be increased by using a po lymeric precursor of higher overall functionality. The reasons for thi s are discussed with reference to pyrolysis mechanisms. In particular, some of the ter-polymeric precursors synthesised with a high yield al so give a high yield on pyrolysis due to the presence of branched stru ctures and potential cross-linking sires. (C) 1998 Elsevier Science Li mited. All rights reserved.