THERMAL AND PHOTOCHEMICAL CONVERSION OF POLY(METHYLSILANE) TO POLYCARBOSILANE

The use of some highly branched soluble copolymers, -[(CH3SiH)(x)(CH3S i)(y)](n)-, as pyrolytic precursors to silicon carbide (SiC) was exami ned. A progressive increase in the ceramic yield with increased branch ing was observed, parallel to a drastic decrease in the soluble polyme r synthetic yield. Poly(methylsilane), PMS, was thermally and photoche mically cross-linked before its conversion to SiC. The changes in the PMS structure were monitored by FTIR and Si-29, C-13, and H-1 NMR spec tra. An increase in the ceramic yields for irradiated polymers was obs erved. This effect was stronger when the polymer irradiation was perfo rmed in the presence of AIBN. The PMS thermolysis was also studied usi ng n-hexane or toluene as solvent, at 70 degrees C, in the presence of AIBN. Toluene showed an inhibiting effect on Kumada rearrangement, wh ile n-hexane was a good solvent to obtain the conversion of PMS to pol ycarbosilane, at a relatively low temperature.