Restricted
by their molecular structure defects, poly(methylphenylsiloxanes) usually
exhibit a relatively low thermal stability, thus limiting their application in high-temperature areas. In this paper, we introduce a cost-effective
synthesis method to prepare poly(methylphenylsiloxanes) (PPMS-M) with
methyl–phenyl mixed cyclic monomers as raw materials. The molecular
structure characterization shows that PPMS-M contain abundant phenyl
groups, and the phenylsiloxane units are evenly distributed among
methylsiloxane segments. The thermal degradation kinetics are systematically
studied with the Flynn–Wall–Ozawa method. It shows that
PPMS-M exhibits much higher degradation activation energy than ordinary
poly(methylphenylsiloxanes) (PPMS-PD) does, which is prepared by 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane
(P3) and octamethylcyclotetrasiloxane (D4).
The thermogravimetry–Fourier transform infrared characterization
shows that the degradation process of the phenyl group in PPMS-M occurs
at temperatures of 100–200 °C higher than those for PPMS-PD.
PPMS-M exhibits good thermal stability and a low glass transition
temperature. Our method would be applied to cost-effective synthesis of other
high-performance functional polysiloxanes.