Development and Characterization of Recyclable Elastomers via Covalent Adaptable Network

Abstract

The inherently high strength, thermal and solvent stability of thermoset is a consequence of the permanent crosslinking between the polymer chains. However, this permanent crosslink is a doubtful advantage; it does provide strength and thermal stability to the polymeric material, but it also makes the material so thermally stable that it cannot be thermally reprocessed. As a result, new type of crosslink has been developed and implemented into polymeric materials, namely dynamic covalent bonding. The use of dynamic covalent bonds in the crosslinking of polymeric material provides the highly sought-after strength, thermal and solvent resistance as a consequence of crosslinking the chains. Furthermore, the dynamic nature of these crosslinks is added to the reprocessability feature to the polymeric materials as a result of the chemically reversible exchange of these bonds. Ultimately, the implementation of the dynamic bond into the crosslinking of polymers create another type of polymer network that are responsive to their environment, commonly known as covalent adaptable networks (CANs). CANs have been implemented widely to improve some polymer networks properties such as reprocessability, recyclability, and self-healability. However, there is still room for improvement in the field of CANs, especially in tuning their mechanical properties i.e., improving tensile strength and elongation while maintaining good dynamicity. In this the dissertation, a fundamental study of the dynamicity of thiol-yne based small molecule models was executed. Furthermore, novel CANs with controllable thermomechanical properties were successfully synthesised and characterised. Finally, a series of novel bio-based CANs with tunable thermomechanical properties were also successfully synthesised and characterised.