Ultrasonic degradation studies of poly(ethylene oxide), poly(ethylene adipate) and poly(dimethylsiloxane)

Ultrasonic degradation studies on solutions of poly(ethylene adipate), poly(ethylene oxide) and poly(dimethylsiloxane) are reported. Measurements of the molar mass distribution using gel permeation chromatography indicate that there is little evidence for degradation in the shorter chain polymer materials. For the higher molar mass polymers, a progressive decrease in the number and weight average molar masses observed and the molar mass distribution was observed to progressively narrow with increase in the ultrasonic irradiation time. For the higher molecular weight polymers, a decrease in the viscosity of polymer solution was also observed with increasing irradiation time. Various mechanisms for the interpretation of the degradation process are considered and it is proposed that the degradation process is in part be connected with the changes that occur in the viscoelastic relaxation spectrum for the polymer solution with changes in the molecular weight distribution of the polymers being irradiated. The proposed mechanism is consistent with the observation of a lower limiting molar mass below which degradation does not occur. (C) 2003 Elsevier Ltd. All rights reserved.