As a result, the reproduction of these reactions is difficult and the progress in the field of photoredox chemistry is hampered by this limitation. However, for most reactions reported in the literature, these parameters are not precisely controlled and recorded. It is well known that the control of light intensity, the exact reaction temperature and other parameters are crucial for the success of a photochemical reaction. Most published photochemical reactions are still not performed under standardized conditions. (2021), in which they use a custom-made multichannel PBR to evaluate several wavelengths at the same time for the photodecarboxylation of palmitic acid using Chlorella variabilis photodecarboxylase. An interesting approach regarding wavelength optimization has been recently published by Winkler et al. (2019) have enumerated the criteria that a PBR using LED as light source should satisfy regarding illumination: 1) The system must be flexible regarding its scalability using a single light source, 2) the light intensity must be variable to be able to understand the optical power requirements of the process, 3) the PBR should have a powerful cooling system, so that photochemical and thermal processes can be decoupled, and lastly, 4) the LEDs must be monochromatic so that the wavelength used for the biotransformation can be identified. 4) Light emitting diodes (LEDs) have been appointed as an optimal solution due to their high light intensity and low heat dissipation, but unfortunately their price is still prohibitive in some cases (Su et al., 2014). Finally, the design of flow reactors is discussed to help newcomers contribute to the current and future developments in the field.
The development of the field is discussed, concluding with the most recent examples on automated polymer synthesis, reactor telescoping and nanoparticle synthesis. In this review we give a comprehensive overview of polymer reactions being carried out in continuous flow reactors to date. The advantages of applying flow chemistry principles for polymer reactions include increased reproducibility and synthetic precision, significant increases in reaction performances for photochemical reactions, the ability to couple reactors to create complex materials in a single reactor pass, as well as the unique combination of online monitoring and machine learning. A wide variety of polymer reactions have been performed in a continuous fashion on small and intermediate scales.
Yet, within the last decade, the field has moved from the rare occurrence of flow reactors to their abundant use today. Accompanied by inline process monitoring, the reactor platform sets an ideal basis for mechanistic studies and process intensification.Ī variation of polymerizations has long been performed in continuous flow reactors on industrial scale comparatively, on smaller scales, continuous polymerization methods have only gained significant attention in recent years. Under standardized conditions, photochemical reactions are enabled in either single‐, multi‐batch or continuous flow mode while preserving the characterized irradiation geometry. A multi‐purpose reactor platform for the application in the field of photochemistry has been developed. Uniting the strengths of the photoreactor platform with an in‐situ monitoring approach permitted reliable kinetic and mechanistic studies.
The versatility of the reactor platform has been tested on a variety of benchmark reactions under batch, multi‐batch and continuous flow conditions. Interchangeable irradiation units and reactor functionalities reduce the necessary equipment for running photochemical reactions to a minimum. Considering the diverse requirements for photochemical reactions, we have developed a multi‐purpose reactor platform that aims for an equally efficient implementation of photochemical reactions under batch and continuous flow conditions. Reactor technology plays a vital role in photochemistry since process efficiency and reproducibility largely depend on the used reactor design.