Ultrasonic degradation of alkyl-substituted polysilanes

The degradation of poly(methyl-n-propylsilane), poly(di-n-butylsilane) and poly(di-n-hexylsilane) by ultrasonic irradiation has been studied in various solvents. The changes in the optical absorption spectra of the polymer solutions and the molecular weight distributions have been followed as a function of time. Although efficient degradation of poly(methyl-n-propylsilane) was observed in CCl₄, the polymer scarcely decomposed in toluene and cyclohexane. The decrease in the molecular weight was initially rapid but slowed with time and reached a limiting value. The rate of degradation and the limiting chain length were dependent on the size of the substituents. Polysilanes with bulky substituents such as poly(di-n-hexylsilane) and poly(di-n-butylsilane) degradated slower than poly(methyl-n-propylsilane) and the degradation yielded higher limiting molecular weights.