ULTRASONIC DEGRADATION OF POLYMER-SOLUTIONS .2. THE EFFECT OF TEMPERATURE, ULTRASOUND INTENSITY AND DISSOLVED-GASES ON POLYSTYRENE IN TOLUENE

Solutions of polystyrene in toluene have been studied as part of a comprehensive study of the parameters affecting the degradation of polymers under irradiation with high-intensity ultrasound. Results are reported which demonstrate the molecular weight dependence of the process and the effect of solution temperature, ultrasound intensity and the nature of dissolved gases on the rate and extent of degradation over a considerably wider range than previously studied. They demonstrate that the limiting molecular weight and polydispersity of the materials can be controlled by suitable manipulation of the experimental conditions. The effects are explained in terms of the influence that each of the parameters has on the shear gradients generated around cavitation bubbles in the solution. The possibility of using the ultrasound process in the control of polymer structure and for the preparation of block copolymers is discussed.