Polysilaethylene , precursors

Interrante and coworkers developed two polysilaethylene precursor systems, which upon pyrolysis gave nearly phase-pure SiC (95-99% SiC) in high ceramic yield (75-90%) (Scheme ll)116. The first procedure begins with a multistep synthesis of 1,1,3,3-tetrachloro-l,3-disilacyclobutane (monomer), 5. Alternately, gas phase pyrolysis will convert 6 to 5. 

To date, two precursor types have been identified that transform to nearly phase pure SiC. These are polymethylsilane (PMS, —Cl I3IISi—) and polysilaethylene (equation 33), which are related by the fact that heating PMS >300 °C transforms it via the Kumada rearrangement7 to polysilaethylene. 

Both PMS and polysilaethylene or polyperhydridocarbosilane have a 1 1 Sit C ratio and in principle are designed to generate phase pure SiC. In practice this is often not the case for a variety of reasons, as discussed below. Several related precursor systems and processing methods that provide essentially phase pure SiC are also discussed below to provide perspective. 

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