A General Strategy for Radical Ring-Opening Polymerization of Macrocyclic Allylic Sulfides

Radical ring-opening polymerization (ROP) is a useful strategy for synthesizing polymers with complex main-chain structures. However, introducing complex functionalities into the polymer backbone via existing radical ROP methods remains challenging. Herein, we report a general strategy for the ring-opening polymerization of macrocyclic allylic sulfides. Modular and scalable syntheses of macrocyclic allylic sulfide monomers are demonstrated. Their polymerization can be performed efficiently under ambient conditions. Regioselective propagation of the thiyl radicals allowed for the construction of various linear main-chain polymers without cross-linking in excellent yields. Density functional theory calculations support that the radical cyclization step is crucial for the regioselectively of the propagating thiyl radical. This work represents a promising advance in radical ROP toward complex main-chain functional polymers.