Flow mediated metal-free PET-RAFT polymerisation for upscaled and consistent polymer production

Four commercially available xanthene based organo-dyes, eosin Y, erythrosin B, phloxine B, and rose bengal, were investigated for their ability to catalyse PET-RAFT polymerisation under different process conditions. The dyes were shown to be efficient photocatalysts under batch and flow conditions without prior deoxygenation, however, polymerisation under flow conditions provided polymers with narrower molecular weight distributions in shorter irradiation times. Additionally, running the flow reactor under fully-continuous or semi-continuous (slug flow) operation led to large discrepancies in product quality (composition and dispersity of synthetic polymers) over the course of the reaction; using the slug flow mode drastically increased the consistency of polymer product compared to the fully-continuous process, and repressed the formation of unwanted high molecular weight products that can potentially cause reactor fouling. The superior product formation under slug flow conditions was attributed to the increase in mixing due to recirculatory fluid flow, which homogenised the residence time distributions of the reaction mixtures.