High Power Ultrasound in Making and Breaking Polymers
G.Price (University of Bath, Bath, UK)
The passage of high power ultrasound through liquids can cause cavitation resulting in the generation of reactive intermediates such as free radicals as well as producing high shear conditions around the collapsing bubble. In heterogeneous systems, efficient mixing and enhanced transport of reagents to and from surfaces can occur. All of these effects can be exploited in polymer chemistry. The oldest known effect is the breakage of long polymer chains in solution when exposed to ultrasound. Recent work in understanding the kinetics of the process and its usefulness in promoting polymer mixing will be described. The usefulness of ultrasound in preparative work will be illustrated by reference to investigation of radical polymerisation using sonoluminescence and spectroscopic measurements, with other applications selected from the preparation of silicon containing polymers by reactions at metal surfaces, emulsion polymerisation processes and the modification of polymer surfaces. The emphasis will be to illustrate how the use of ultrasound allows us to control and/or modify the reactions.
Section : 11