Utilization of carbon disulfide (CS2), a low-cost and sulfur-rich one-carbon (C1) feedstock, for making sulfur-containing polymers is important for both polymer chemistry and applied environmental science. However, the production of well-defined sulfur-containing polymers from CS2 and epoxides remains a key challenge. Here, we report a robust coupling reaction of CS2 and epoxides for chemoselectively producing poly(thioether)s and carbonyl sulfide (COS) in one pot. The resultant polymer has exclusive thioether units and a thiol (−SH) terminal. This route takes advantage of oxygen/sulfur exchanges through two consecutive reactions, i.e., cycloaddition of CS2 to epoxides and dethiocarboxylative ring-opening polymerization of the generated cyclic dithiocarbonates. The process can be conducted in ambient air with several commercially available organic bases as catalysts (initiators) and extended to a variety of epoxides, yielding COS and diverse poly(thioether)s with tens of grams. This work furnishes an original and practical strategy for utilizing CS2 as a sulfur feedstock in polymer synthesis.
Graphical The synthesis of poly(propylene monothiocarbonate)s from COS/PO copolymerization under mild conditions using the heterogeneous catalyst CoCo-PBA is reported. This study demonstrates the superiority of a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co 3 [Co(CN) 6 ] 2 ), a typical cobalt Prussian Blue Analogue (CoCo-PBA) that catalyzes the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO) to produce poly(propylene monothiocarbonate)s (PPMTC). The number-average molecular weights of the PPMTC were 66.4 to 139.4 kg/mol, with a polydispersity of 2.0–3.9. The catalyst productivity reached 1040 g polymer/g catalyst (12.0 h). The oxygen-sulfur exchange reaction (O/S ER), which would generate random thiocarbonate and carbonate units, was effectively suppressed, and thus the selectivity of the monothiocarbonate over carbonate linkages was up to >99%. It was shown that no cyclic thiocarbonate byproduct was produced during the heterogeneous catalysis of COS/PO copolymerization using CoCo-PBA as the catalyst. The content of monothiocarbonate and ether units in the copolymer chain could be regulated by tuning the feeding amount of COS.
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