The alteration of molecular weight distributions of polymers by ultrasonic energy

Methods of producing selected monodispersed samples of addition polymers have gained importance in many phases of polymer research. The ability of cavitation resulting from intense ultrasonic energy selectively to degrade polymers by fracturing longer chains at a faster rate than shorter chains is investigated as a means of sharpening molecular weight distributions. Conflicting degradation theories and experimental findings are reviewed, and new degradation models based on reasonable degradation mechanisms are developed. An IBM 7040–1401 computer was used to simulate degradation for these models. The solutions show in detail how molecular weight distributions are shifted and altered, depending on the kinetic expression used. In all the cases investigated monodispersity is first seen to decrease and then increase as a function of time.