Anionic Ring‐Opening Polymerization of Thionolactones: Status and Perspectives

Compared with the extensively studied radical and cationic ring-opening polymerizations (ROP), the behavior of thionolactones under anionic conditions (aROP) has long remained unclear, only recently coming to light through key breakthroughs. The aim of this Perspective is threefold: (1) to highlight the importance of sulfur-containing polymers and the historical challenges in accessing them; (2) to summarize state-of-the-art initiating systems that enable precise control over molecular weight and dispersity while allowing complete selectivity between thiocarbonyl retention and S/O isomerization; and (3) to offer perspectives on the broader development of thionolactone aROP, with a focus on mechanistic understanding, monomer design, and copolymerization strategies.