Continuous synthesis of grafted polyesters through successive photocontrolled BIT-RDRP and ROP strategies in flow tube reactors

Abstract

Graft copolymers are of great interest for their unique physicochemical properties, and have been extensively applied in many fields. In this work, a facile and efficient strategy for preparing grafted polyesters was developed by the combination of photocontrolled bromine–iodine transformation reversible-deactivation radical polymerization (BIT-RDRP) and ring-opening polymerization (ROP) in flow reactors at room temperature for the first time. Specifically, polymethacrylate macroinitiators were synthesized by the copolymerization of butyl methacrylate (BMA) and 2-hydroxyethyl methacrylate (HEMA) via photocontrolled BIT-RDRP in the first tube, which are employed directly for 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (TBD)-catalyzed ROP to provide tailored grafted polyesters in the second tube. The macromolecular architectures can be adjusted by variation of the retention time and the feed ratio of BMA to HEMA (from 0/100 to 70/30). Importantly, the polymerization rates are improved significantly, 2.2 and 1.2 times higher for BIT-RDRP and ROP respectively than that in batch reactors, and grafted polyesters with controlled molar mass and relatively narrow dispersity (Đ ≤ 1.30) are achieved. Furthermore, the employment of flow tube reactors greatly simplifies the operation process, which facilitates the scale-up production.