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.