Microstructured reactors for polymer synthesis: A renaissance of continuous flow processes for tailor-made macromolecules?

Organic synthesis in microfluidic devices has attracted increasing interest in recent years. However, little efforts had been undertaken to exploit this novel technology for polymer chemistry until several recent studies demonstrated the interesting potential of microreactors for the synthesis and modification of polymers. In fact, anionic polymerizations in continuous capillary flow-tube systems were established already in 1962 in pioneering work by Szwarc. Subsequent work focused on detailed kinetic analyses in such reactors. The present article explores different current strategies developed by several research groups to realize bulk and solution polymerizations using continuous flow microreactors. Inherent benefits and limitations of these systems compared to traditional laboratory set-ups are discussed. We sent a variety of recent pioneering and advanced approaches to realize free radical, controlled radical, cationic and anionic polymerizations in microtechnological reaction devices. In some cases, surprisingly narrow molecular weight distributions have been obtained, demonstrating the promising potential of this approach for the tailoring of polymer structures.