DescriptionDynamic covalent chemistries have been widely used to create reversibly crosslinked polymer networks that show improved (re)processability compared to permanently crosslinked networks. In dissociative networks, the crosslink density of the polymer network decreases with increasing time and intensity of the application of the adequate stimulus, such as heat or light, resulting in a dramatic change in the viscoelastic behaviour. The thermoreversible Diels-Alder reaction between furan and maleimide is the most widely studied dynamic covalent chemistry. Heating the thermally reversible polymer networks shifts the reaction equilibrium towards the gradual breaking of the cycloadduct crosslinks, eventually leading to degelation of the network structure. This reversible gel transition was employed to create complex objects using many industrially relevant manufacturing techniques such as casting, moulding and additive manufacturing. In contrast, associative networks do not show a net change in network connectivity. The rate at which a certain functional group exchanges with existing covalent bonds changes upon the increase of the stimulus intensity, allowing reprocessing.
Dynamic covalent chemistries have also become very popular to create self-healing materials that are able to reform broken covalent bonds to recover their functional properties. These materials extend the service lifetime of structures and systems, thus increasing the durability and sustainability of the derived objects. The self-healing property has been demonstrated and validated in applications such as coatings, composites and robotics. The thermomechanical and viscoelastic behaviour and the healing performance of the materials can be tuned to the application’s requirements using accurate knowledge of the reaction kinetics and thermodynamics and structure-property relations.
|26 May 2022
|Polymers 2022: Health of the people, health of the planet
|Degree of Recognition