The incorporation of sulfur centres into the polymer main chain rationally offers distinct material properties and functions associated with the periodic trends of the main-group elements. The altered electronic nature of sulfur containing polymers compared to their lighter oxygen analogues causes amongst others degradability benefits, the potential to scavenge heavy metal contaminants, high refractive indices, stimuli responsiveness in drug delivery systems and enhanced semi-crystallinity. Moving from oxygenated to sulfurated polymers can furthermore be used to tune the (de)polymerisation equilibria of polymers to facilitate chemical polymer recling. -10 Furthermore, using monomers which can be directly sourced from elemental sulfur (such as CS2 from S8 and methane) is also relevant in the context of S8 utilization, a waste product of the petrochemical industry being produced at an annual megaton surplus. Sulfur containing polymers are often synthesized by condensation or ring-opening polymerisation (ROP) methods, which can require multi-step monomer synthesis and do not give easy access to many polymer structures. An increasingly popular method for the synthesis of heteroatom containing polymers is the ring-opening copolymerisation (ROCOP) of a strained heterocycle with heteroallenes. Having gained prominence for the selective copolymerisation of CO2 with epoxides or oxetanes to polycarbonates, ROCOP cannot only make use of under-utilized monomer feedstocks but also produce previously inaccessible polymer structures. Taking this methodology to the arena of sulfurated polymers, ROCOP of carbonyl sulfide COS with epoxides or oxetane represents a well-established route to selectively yield poly(monothiocarbonates) (Figure ). Yet this ROCOP requires specialised steel reactor setups to safely handle highly toxic, flammable and gaseous carbonyl sulfide as well as commercial access to high purity COS (which is for example currently not the case in Europe) limiting the utility of this ROCOP in standard research laboratories. Using the liquid heavier homologue CS2 is substantially simpler as it can be employed as a cosolvent and in principle allows access to copolymers with even higher sulfur ranks. However, the ROCOP of CS2 with oxygen containing heterocycles has so far been plagued with numerous side reactions as show in Figure