Ring-Opening Terpolymerisation of Elemental Sulfur Waste with Propylene Oxide and Carbon Disulfide via Lithium Catalysis.

Elemental sulfur, a waste product of the oil refinement process, represents a promising raw material for the synthesis of degradable polymers. We show that simple lithium alkoxides facilitate the polymerisation of elemental sulfur S with industrially relevant propylene oxide (PO) and CS (a base chemical sourced from waste S itself) to give poly(monothiocarbonate-alt-S) in which x can be controlled by the amount of supplied sulfur. The in situ generation of thiolate intermediates obtained by a rearrangement, which follows CS and PO incorporation, allows to combine S and epoxides into one polymer sequence that would otherwise not be possible.

Precise construction of weather-sensitive poly(ester--thioesters) from phthalic thioanhydride and oxetane.

We report the selective ring opening copolymerisation (ROCOP) of oxetane and phthalic thioanhydride by a heterobimetallic Cr(III)K catalyst precisely yielding semi-crystalline alternating poly(ester--thioesters) which show improved degradability due to the thioester links in the polymer backbone.

Precise cooperative sulfur placement leads to semi-crystallinity and selective depolymerisability in CS/oxetane copolymers.

CS promises easy access to degradable sulfur-rich polymers and insights into how main-group derivatisation affects polymer formation and properties, though its ring-opening copolymerisation is plagued by low linkage selectivity and small-molecule by-products. We demonstrate that a cooperative Cr(III)/K catalyst selectively delivers poly(dithiocarbonates) from CS and oxetanes while state-of-the-art strategies produce linkage scrambled polymers and heterocyclic by-products. The formal introduction of sulfur centres into the parent polycarbonates results in a net shift of the polymerisation equilibrium towards, and therefore facilitating, depolymerisation.