Degradation of Poly(ethylene oxide) in Aqueous Solutions by Ultrasonic Waves

The effects of ultrasonic waves on aqueous solutions of poly(ethylene oxide) (PEO) are reported. Static and dynamic light scattering measurements are performed on dilute irradiated solutions for various exposure times in order to characterize the polymer species that are present in the solutions at the end of the process. A progressive aggregation of the polymer chains is observed for the sample having the lower weight-average molecular weight (M-w=6 kDa). These aggregates are stable but they are break by addition of sodium chloride (NaCl) in the aqueous solutions and the initial chains are recovered. The high molecular weight sample (M-w = 2 X 10(3) kDa) shows a different behavior under irradiation. The molecular weight of the processed polymer is lower than the initial molecular weight. However by addition of molecular weight of the species decreases. This indicates that, in a first time, the large polymer chains are cut in smaller chains but furthermore they aggregate in stable clusters that are break by NaCl addition. The duster formation is imputed to the instantaneous local increase of concentration of the hydrophobic -CH2-CH2- groups that belong to different PEO chains in the field of the ultrasonic waves.