Ultrasonic degradation of polysiloxane solutions

Fractions of dimethylsiloxane polymer with viscosity‐average molecular weights from 2.4 × 105 to 1.3 × 106 were dissolved in toluene in concentrations from 0.01 to 1.0 g./dl. These solutions were subjected to ultrasonic degradation at 20,000 cps for periods extending to as much as 960 min. in a water‐cooled reaction vessel. Gel permeation chromatography shows that samples with different initial distributions approach the same distribution after 120 min. of degradation. Dilution of the polymer from 1.0 to 0.01 g./dl. more than triples the degradation per gram of polymer but requires 10 times as much energy per gram of polymer to degrade from a number‐average molecular weight of 106 to 105. Increasing the power input from 36 to 72 w. almost doubles the degradation rate per gram of polymer.