DUAL-PHOSCAT · Multi-functional DUAL PHOSphorus-based organoCATalysts for stereoselective ring-opening polymerisation

Multi-functional DUAL PHOSphorus-based organoCATalysts for stereoselective ring-opening polymerisation

Summary of the context and overall objectives of the project: Aliphatic polyesters are a highly important class of biodegradable polymers on account of their controllable materials and degradation properties that enable their use in applications as varied as commodity plastics (such as in packaging or fibers) or as speciality plastics (e.g. in biomedical devices). The micro and macro-structure of a polymer define the physical properties and potential applications. Thus, the synthesis of such macromolecules must be controlled to obtained materials with predictable and desired properties. The ring-opening polymerisation (ROP) of cyclic (di)esters in the presence of a catalyst/initiator (Cat/I) system readily enables the synthesis of polyesters with well-defined structure. The ROP of LA has been studied extensively, largely as a consequence of the production of lactide (LA) from renewable resources and the widespread study of polylactide (PLA) materials across a wide range of application areas. However, challenges still remain in which targeted catalyst design presents the most favourable solutions. Achieving stereocontrol in polymerisation of chiral monomers has been one of the most important goals since the early 90’s. Apart from the exciting challenge of accomplishing the perfect control in enantioselective reactions, another important aspect has also stimulated this field: the properties of the polymer are highly dependent on the microstructure of the macromolecule and controlling the stereoselectivity gives access to materials with precise and finely-tuned properties for specific applications. Numerous efficient organometallic initiators have been reported for the stereoselective ring-opening polymerization of cyclic esters but most of them are air and moisture sensitive compounds and should be used under strictly air and water free conditions that is an important drawback to their industrial applications. Organocatalysts have emerged as a viable alternative to organometallic initiators in ROP processes. These catalysts result in polymers that are free of residual metal contaminates as desired for specific biomedical or microelectronic applications. To date there are very few reports of stereocontrolled organocatalytic ROP under practical conditions (room temperature or above, in bulk etc.). To advance the field, new tuneable chiral organocatalysts are required. The project will pave the way in the design of tunable polymerisation organocatalysts for the preparation of polymers with controlled tacticity such as polylactide. The research project proposed to develop chiral tunable phosphorus-based organocatalysts possessing chiral functionalities such as thioureas for dual activation of both the monomer(s) and the initiator, to overcome these challenges.

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