Self-healable, reprocessable and anti-flammable eugenol-derived covalent adaptable thermosets based on dynamic covalent boronic esters and thiol–ene click chemistry†

Abstract

Due to their excellent properties, thermosetting polymer materials have been widely used in many fields. Owing to the restriction of the crosslinked network, traditional thermosetting polymer materials exhibit insolubility and immiscibility. Therefore, the reprocessing of thermosetting polymer materials is a great challenge. With the depletion of petroleum-based resources, the utilization of natural resources for the preparation of bio-based thermosetting polymer materials is a major trend. In this study, eugenol-based covalent adaptable thermosets were prepared via UV curing and thermal curing according to thiol click chemistry. The mechanical properties of the eugenol-based covalent adaptable thermosets, which are better than those of the control sample, can be regulated according to the components. The eugenol-based covalent adaptable thermosets exhibited excellent transparency and UV shielding properties. The introduction of a dynamic covalent boronic ester (BSH) promoted the formation of residual char and enhanced the fire safety of the eugenol-based covalent adaptable thermosets. Owing to the dynamic borate ester bonds in the cross-linked network, the eugenol-based covalent adaptable thermosets exhibited significant stress relaxation behavior, and excellent shape memory function and self-healing properties. The samples were reprocessed at 100 °C several times. After three cycles of pulverizing and hot pressing, the recovery ratio of tensile strength of the reprocessed samples remained above 85%. This study provides a novel strategy for preparing self-healable, reprocessable and anti-flammable covalent adaptable thermosets with tunable mechanical properties.