Rational Entry to Cyclic Polymers via Thermally Induced Radical Ring-Expansion Polymerization of Macrocycles with One Bis(hindered amino)disulfide Linkage

Recent advances in polymer chemistry have made the synthesis of polymers with various topologies possible, albeit effective synthetic routes to cyclic polymers remain limited. In this study, cyclic polymers were synthesized via a simple heat-induced ring-expansion polymerization of macrocyclic monomers with one bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) linkage. The cyclic topology of the resulting products was confirmed by a variety of analytical techniques, including electrospray ionization time-of-flight mass spectrometry, proton nuclear magnetic resonance, size exclusion chromatography (SEC), and SEC equipped with multiangle light scattering. Furthermore, the synthesis of cyclic random copolymers and functionalized cyclic polymers was also accomplished. This method represents a simple route for the insertion of functional groups into cyclic copolymers, which may significantly advance their applications.