RAFT Step-Growth Polymerization via 'Grafting Through'

Graft polymers with degradable backbones and precisely tunable side chains are highly desirable for advanced functional materials, particularly in biomedical and stimuli-responsive systems. Herein, we report a versatile strategy to synthesize degradable graft polymers via a reversible addition-fragmentation chain transfer (RAFT) step-growth polymerization approach using bifunctional poly-(methyl acrylate) (PMA) macromonomers and a bifunctional vinyl monomer. The polymerization proceeds through an A₂ + B₂-type polymerization mechanism, wherein the steric hindrance from macromonomers is effectively alleviated by incorporating a small-molecule RAFT agent as a comonomer. The resulting graft copolymers exhibit tailorable side-chain lengths and tunable rheological properties. Notably, the polymer backbones feature dual stimuli-responsive degradability enabled by xanthate and ester linkages, allowing stepwise degradation via aminolysis and hydrolysis. Furthermore, RAFT functionalities embedded in the backbone allow postpolymerization chain expansion, offering control over both the backbone architecture and graft density. This work provides a modular and robust platform for engineering degradable graft polymers with programmable architectures and multifunctionality suitable for applications in drug delivery and smart materials.