| Abstract
| - Reflux-treated poly(methylsilane) (PMS) at 420−570 K improves its ceramic yielddramatically. This efficient process was investigated by TG, GC, 29Si, 13C, and 1H NMR,and FT-IR methods. The structural transformation process of the PMS polymer consists ofthree stages. In the first stage below 500 K, PMS forms Si−Si3 cross-link units predominantlyby evolving MeSiH3. This process may proceed mainly via silylene formation. The Si−Sicross-link structure leads to a high ceramic yield up to 89%. In the second stage around 625K, thermal rearrangement of the Si−Si3 units to Si−CH2−Si units (Kumada rearrangement)begins to convert the polymers into polycarbosilanes. The third stage occurs above 673 Kwhere almost all polymer units are converted into SiC4 units. Evolution of H2 and CH4 beginsin the second stage and becomes the dominant process in the third stage.
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