The degradation of narrow molar mass distribution samples of polystyrene dissolved in toluene when exposed to ultrasound are reported. The change in molar mass on exposure to the ultrasound was monitored by use of gel permeation chromatography and solution viscosity measurements. Dynamic response of the polymer molecules in solution to the ultrasonic perturbation is calculated using a modification of the Wang-Zimm theory. A good correlation between the decrease in the energy absorption predicted by theory and the decrease in the rate of degradation was observed. It is proposed that the degradation process induced by ultrasonic degradation be intimately connected with the viscoelastic response of a polymer molecule in dilute solution and is not just a consequence of the cavitation process.
- polystyrene viscoelastic relaxation