“…12 In addition to the many metal-based catalysts, 13 a variety of simple organocatalytic systems including 4-dimethylaminopyridine (DMAP), 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 4-pyrrolidinopyridine (PPY), ureas, 14 thioureas (TU), 15 N-heterocyclic carbenes as well as various phosphines, phosphazenes 16 and organic phosphoric acids 17 have been shown to promote ROP under mild and metal-free reaction conditions. 18 Typically, cyclic carbonates for ROP are 6-membered rings though there are examples of 7-, 19 8-20 and highly strained 5-21 membered ring monomers. The usually low ring strain of 5-membered cyclic carbonates often means that forcing ROP conditions are required, which result in decarboxylation and ether linkages in the polymer backbone, detrimental to its physical properties.…”