Generation of radicals by ultrasound

Sonic waves comprise linear propagation of regions of compression and rarefaction, and are normally quite harmless. The systems normally adjust in-phase or with a lag time depending on the frequency, and the laws of thermodynamics are obeyed (Blandamer, 1973). However, at ultrasonic frequencies, if the power is increased, micro-cavita- 

The power of ultrasonic generators is often in the region of 105 Wcm-3. This is sufficient to induce cavitation and generate water or other radicals, and hence the widespread use of ultrasound in medicine should be a matter of possible concern. 

The most obvious method for radical generation is to heat molecules until the bonds begin to break. 

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Emulsion Polymerization. The generation of radicals by ultrasound can also be applied in emulsion polymerization, which comprises a free-radical polymerization in a heterogeneous reaction system, yielding submicrometer polymer particles in a continuous aqueous phase. In literature a number of publications have appeared over the years on the application of ultrasound in emulsion polymerization (36-46). Ultrasoimd can be applied both for emulsification purposes as well as at higher conversions in the emulsion polymerization process (see Heterophase Polymerization). 

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