Flow RAFT Step-Growth Polymerization

Reversible addition–fragmentation chain transfer (RAFT) step-growth polymerization offers a powerful platform for constructing degradable polymers with precise functional group incorporation. However, conventional batch processes are limited by slow kinetics, light attenuation, poor temperature control, and inefficient mixing, particularly in photoinitiated systems. Herein, we report the implementation of RAFT step-growth polymerization under continuous-flow conditions to overcome these limitations. Using bifunctional vinyl ester and bifunctional xanthate RAFT agents as monomers, we demonstrate that flow processing significantly accelerates polymerization rates, achieving higher monomer conversion and molecular weights in drastically reduced times compared to batch systems. Chain extension modules were successfully integrated in-line, enabling the continuous synthesis of graft and multiblock poly(vinyl acetate) (PVAc). To further address the challenges of laminar flow mixing, we developed a high-borosilicate glass reactor with an engineered geometry that enhances micromixing and light penetration, resulting in improved monomer conversion, higher molecular weights, and narrower dispersities. This work establishes a versatile, modular, and scalable strategy for the flow-enabled synthesis of functional sequence-controlled polymers through RAFT step-growth polymerization.