Ionic polymerizations in microstructured reactors

Organic synthesis in microfluidic devices ("microreactors") has attracted enormous interest in recent years. Particularly the highly efficient heat and mass transfer as well as extremely fast mixing of reactants renders microstructured reactors superior to conventional set-ups for many synthetic applications. Depending on the apparatus, products are accessible from the microgram- to the multi-kilogram scale in continuous flow. Ionic polymerization reactions commonly proceed highly exothermic and require efficient mixing processes in order to afford well-defined products. The present article explores different modern strategies developed by several research groups to carry out bulk and solution polymerizations using continuous flow reactors based on the mixing of reactants in microstructured devices. We describe a variety of recent pioneering approaches to realize cationic and anionic polymerizations in microdimensional reaction systems. In some cases, remarkably narrow molecular weight distributions have been obtained, demonstrating the promising potential of this approach for the tailoring of polymer structures.