Scalable preparation of cyclic polymers by the ring-closure method assisted by the continuous-flow technique

The endless molecular topology endows cyclic polymers with fascinating physical properties and applications. As a powerful strategy for the preparation of well-defined cyclic polymers, the current ring-closure methods have an inherent disadvantage of low production efficiency under the classic batch reaction conditions due to the requirement of ultralow reaction concentration for ring-closing linear polymer precursors. Assisted by the continuous-flow technique, we developed an efficient and practical way to ingeniously solve this essential problem and successfully produce cyclic polymers on a large scale by a light-induced ring-closure method for the first time. In addition, due to the large surface-to-volume ratio of the flow reactor, the continuous-flow technique provides the light-induced ring-closing reaction with more uniform light irradiation and transmission, resulting in a significantly increased reaction efficiency compared to that from the classic batch reaction conditions.