Ultrasonic depolymerization

In this study the, ultrasonic depolymerization of dilute polyacrylamide solution was realized. The degradation (depolymerization) of polymers by the action of temperature, light, various chemical reagents and ultrasound has proven to be a subject of great potential application and academic interest. The ultrasonic depolymerization (chain scission) of polymers in solution, unlike other degradation processes, is a nonrandom process in which the scission of polymer chains occurs preferentially near the middle of the chains. The exact mechanism of ultrasonic chain scission is still some debate, however, it is generally agreed that hydrodynamic forces may originate as a result of ultrasonic cavitation. During the process of sonication, only most susceptible chemical bond breaks and ultrasound does not lead to side chain reactions or to existince of momoner units. In general terms, in chain scission, the molecular weight of polymers decrease and eventually approaches a limiting molecular weight and limit viscosity. Therefore, a controlled reduction of the molecular weight of polymers is possible. The study of the kinetics of ultrasonic chain scission is important in understanding and to be able control the underlying mechanisms of scission. Until recently it was difficult to study of evolution of the molecular weight in time. Traditionally, in ultrasonic chain scission experiments, the measurement of the molecular weight has been performed by sequential sample technique in which is long and requiring much effort. Also, experimental errors did not allow one to discriminate between various theoretical models. The purpose of this study is to bring the power of the continuous monitoring method using measurement of viscosity to study of ultrasonic polymer degradation in solution. This method gives the viscosity at every moment of the scission process and make possible to review theoretical models of chain scission and compare their predictions. Key Words: Ultrasound, continuous monitoring method, degradation of the polymer.