Amine-Activated Ring-Opening Polymerization of 1,2-Dithiolane in a Cascade Fashion and Organocatalyzed Pendant Modification: A Path to Functional Dynamic Covalent Poly(disulfide)-Based Macromolecules

Dynamic covalent poly(disulfide)s are regarded as sustainable intelligent materials for the future because of their dynamicity and recyclability. Consequently, establishing a comprehensive process for the synthesis of poly(disulfide)s with varied structures and functionalities is highly valuable. This work describes a versatile and efficient cascade ring-opening polymerization (ROP) methodology and postpolymerization route for the synthesis of a library of functional poly(disulfide)s with structural diversity. Here, an amine activates a dormant thiolactone ring to produce a thiolate anion initiator, which subsequently opens the pentafluorophenyl ester (PFP-ester)-containing cyclic disulfide (1,2-dithiolane ring) monomer, thereby propagating polymerization at room temperature under open-air conditions. This cascade ring-opening approach facilitates one-step, in situ dual modification at the polymer chain end, thereby enabling pendant modification with both alcohols and amines through organocatalyzed transesterification and amidation, respectively, at room temperature. As a result, the polymerization approach combined with postpolymerization pendant modification allows multifunctionalization at the same polymer chain of poly(disulfide)s. The room-temperature and open-air mild reaction conditions for the polymerization and postpolymerization modification (PPM) protected the integrity of the delicate disulfide bonds. Previously, postpolymerization was largely unexplored for synthesizing a series of pendant ester and amide-functionalized poly(disulfide)s from a common, end-modified precursor poly(disulfide)s. However, this is now established in the current work through a meticulous design of the monomer and polymerization methodology. We anticipate that this versatile and convenient platform will provide access to numerous functional dynamic covalent poly(disulfide)s via minimal synthetic steps.