Sustainable polyester vitrimer capable of fast self-healing and multiple shape-programming via efficient synthesis and configuration processing

Abstract

Considering that environmental friendliness and energy conservation are becoming crucial, it is urgent to advance the sustainability of materials in terms of their lifecycle, including synthesis, processing, and application. Herein, covalent adaptable networks were constructed in a polyethylene terephthalate (PET) matrix via a green, external-catalyst-free method within only 8 min, which was realized by sequential transesterification and crosslinking reaction. This synthesis is environmentally friendly given that no toxic solvents or external catalysts are required, and it avoids energy waste. Meanwhile, the vitrimer exhibited an extremely fast relaxation time of 4.8 s, which was realized through the synergistic catalysis of the tertiary amine structure and neighboring group participation. Therefore, the vitrimer could readily change its configuration via fast exchange reactions during processing, which eliminated the residual stress and suppressed the molecular-chain orientation, avoiding shrinkage and warpage. Further, the vitrimer has potential sustainable applications in repairability and shape memory, where on the one hand, due to its stable state resulting from configuration-change foaming processing, the vitrimer foam has attractive self-healing behavior, which is the first time this is reported for foam materials, whereas other foams tend to shrink in the melt state, and hence fail to realize self-healing. On the other hand, due to the quick rearrangement of the crosslinking networks, the obtained vitrimer could be rapidly shape-programmed repeatedly, where its shape-memory behavior could be strengthened or erased by the synergistic effects of its covalent adaptable networks and physical crystalline networks, making it more regulable and concealed in encryption application. Briefly, the synthesis, processing, and application of this vitrimer are constructive to guide the design of novel polymers with improved performance and sustainability.