A chiral thiourea and a phosphazene for fast and stereoselective organocatalytic ring-opening-polymerization of racemic lactide

Mohamed Samir Zaky (1) , Anne-Laure Wirotius (1) , Olivier Coulembier (2) , Gilles Guichard (3) , Daniel Taton (1)

1 Team 1 LCPO : Polymerization Catalyses & Engineering
2 CIRMAP - Centre d'Innovation et de Recherche en Matériaux Polymères
3 CBMN - Chimie et Biologie des Membranes et des Nanoobjets

Control of stereoregularity is inherent to precision polymerization chemistry for the development of functional materials. A prototypal example of this strategy is the ring-opening polymerization (ROP) of racemic lactide (rac-LA), a bio-sourced monomer. Despite significant advances in organocatalysis, stereoselective ROP of rac-LA employing chiral organocatalysts remains unexplored. Here we tackle that challenge by resorting to Takemoto's catalyst, a chiral aminothiourea, in the presence of a phosphazene base. This chiral binary organocatalytic system allows for fast, chemo- and stereoselective ROP of rac-LA at room temperature, yielding highly isotactic, semi-crystalline and metal-free polylactide, with a melting temperature as high as 187 °C.

Domaines: Polymères; Catalyse

Mohamed Samir Zaky, Anne-Laure Wirotius, Olivier Coulembier, Gilles Guichard, Daniel Taton. A chiral thiourea and a phosphazene for fast and stereoselective organocatalytic ring-opening-polymerization of racemic lactide. Chemical Communications, 2021, 57 (31), pp.3777-3780. ⟨10.1039/d0cc08022e⟩. ⟨hal-03274815⟩