Surviving radicals: Promises of a microwave effect on miniemulsion polymerization for technical processes

Rapid heating in a microwave oven has unexpected effects on free radical miniemulsion polymerization: After a temperature pulse of less than 20 s, ultra-high molecular weight polystyrene was yielded at a conversion larger than 40%. These results may be explained with the model of surviving radicals according to which single radicals remain active inside the confined reaction space of latex particles even after the emulsion has left the microwave oven. In the pure environment of a 100 nm droplet, they cannot terminate and will polymerize all the monomer within a droplet. In this contribution, we summarize the concept of surviving radical polymerization and present recent results on the effects of radical-active additives and the development of a tube reactor for continuous microwave-assisted processing. These investigations highlight the potential of this method for industrial applications.