THERMAL-DEGRADATION OF POLYSILOXANES .2. POLY(METHYLPHENYLSILOXANE)

Thermal analysis demonstrates that poly(methylphenylsiloxane) is thermally more stable to weight loss than poly(dimethylsiloxane). The stability decreases with increasing molecular weight and with replacement of terminal hydroxyl by trimethylsilyl groups. The principal product of thermal degradation is a mixture of all possible stereoisomeric cyclic trimers and tetramers together with small amounts of two more complex oligomers and pentamer. Benzene is also a significant product, the proportion increasing with decreasing molecular weight and increasing temperature. These and other observations are discussed from a mechanistic point of view. © 1979.