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Sequence Selective Ring-Opening Terpolymerisation of Elemental Sulfur Waste

Elemental sulfur, a byproduct of the oil refining process, represents a promising raw material for the synthesis of degradable polymers. Utilizing an emerging approach called sequence-selective terpolymerization, we show that simple lithium alkoxides can catalyze the polymerization of elemental sulfur (S₈) with industrially relevant propylene oxide (PO) to yield poly(monothiocarbonate-alt-Sₓ) or poly(ester-alt-Sₓ), where x can be controlled by the amount of sulfur supplied. The in situ generation of thiolate intermediates, formed through a rearrangement, enables the integration of S₈ and epoxides into a single polymer sequence—something otherwise not achievable.

The mechanistic basis for sequence selectivity is discussed, with both kinetic and thermodynamic factors facilitating this novel catalysis. Due to the dynamic nature of sulfur–sulfur bonds, the polymer can undergo skeletal editing and, after crosslinking, can function as a dynamic covalent network useful in thermally reprocessable adhesives. This study illustrates how mechanistic insights can allow the combination of intrinsically incompatible building blocks, advancing sulfur waste utilization.

REFERENCES

[1] S. M. Rupf, P. Pröhm, A. J. Plajer* Chem. Sci. 2022, 13, 6355-6365

[2] P. Deglmann, S. Machleit, C. Gallizioli, S. M. Rupf, A. J. Plajer* Cat. Sci. Tech. 2023, 13, 2937-2945

[3] C. Gallizioli, D. Battke, H. Schlaad, P. Deglmann, A. J. Plajer* Angew. Chem. Int. Ed. 2024, e202319810

[4] C. Gallizioli, P. Deglmann, A. J. Plajer* in preparation