A Route to Sulfur‐Containing Polymers via FeFe‐DMCC‐Catalyzed Copolymerization of Propylene Oxide and Carbonyl Sulfide

Abstract This study investigates the development of the iron‐based catalyst FeFe‐DMCC for the efficient copolymerization of carbonyl sulfide (COS) and propylene oxide (PO), leading to the production of poly(propylene monothiocarbonate)s (PPMTC). The resulting polymers exhibit number‐average molecular weights ( M n ) ranging from 36.6 to 91.8 kg mol −1 , with polydispersity indices ( Đ ) between 1.7 and 4.8. The FeFe‐DMCC catalyst demonstrated exceptional performance, achieving polymer yields of up to 1058 grams per gram of catalyst within a 12‐h reaction period. A significant breakthrough in this work is the catalyst's ability to effectively suppress the oxygen‐sulfur exchange reaction (O/S ER), a side reaction that typically generates mixed linkages. Instead, the process achieved outstanding selectivity, exceeding 99%, for monothiocarbonate units, with no formation of cyclic thiocarbonate byproducts. This remarkable control underscores the catalyst's efficiency in producing clean, well‐defined polymers. Additionally, the copolymer composition, particularly the ratio of monothiocarbonate to ether units, can be finely tuned by varying the COS feed ratio, enabling precise customization of the polymer's properties. These findings establish FeFe‐DMCC as a highly effective and selective catalyst for COS/PO copolymerization, offering a pathway to produce high‐quality PPMTC with tailored characteristics and minimal byproduct formation. This work represents a significant advancement in sustainable materials development.