Flow chemistry has in the past 10-20 years found entry into academic laboratories all over the world, and in all domains of research. The reason for this progress is that flow reactors possess some inherent advantages that classical batch-wise chemistry, or flasks in other words, do not. Flow reactors are usually attributed to very good mass and temperature transport. What sounds very technical (and it is technical), has very practical consequences. Reactions proceed under highly isothermal conditions, and exothermicity has little influence on the reaction since heat is dispersed efficiently. This is in contrast to flasks and batch production, where headspace plays an important role, heating and cooling is inefficient, and exotherms result in fast overheating of reactions. In academic labs we use the isothermicity in order to avoid side reactions, and to increase the yield of reactions. In industrial setting, other advantage becomes more important though. This is the scalability of processes. Since thermal characteristics are close to ideal, reactions can be quickly scaled from laboratory to pilot scale and finally to production scale. Industrial translations, which usually can take years to achieve, suddenly become available in short amount of time. At the same time, continuous flow reactors can be built in a highly modular way, giving access for example to plant-on-a-truck concepts, where production capacity can be quickly built at the point where products are required.

These advantages aren’t anything new – any chemical engineer will learn this in their 101 courses. In fact, all materials made at very large scale – bulk commodities – are typically produced in continuous fashion for exactly the reasons described above. What is new though is that flow reactors are also used for fine chemical synthesis, or synthesis of very valuable materials at relatively small scale. For example, the pharmaceutical industry is rapidly switching from batch-wise to continuous flow conditions. These reactors are easier to operate, have a smaller footprint, are often more energy efficient and thus inherently greener, and provide improved process reliability. In fact, advantages are so significant that the FDA has already issued the intent to move all pharmaceutical production into flow in the near future. For polymer research this means that flow chemistry in production is mostly interesting in areas of high-added value materials, and speciality polymers. This is particularly true for example for block copolymers, but also nanoparticles and organic electronic materials.

by Prof. Tanja Junkers, Polymer Reaction Design Group, Monash University (Australia)