Polyurethane toughened covalent adaptive networks epoxy composite based on thermoreversible Diels‐Alder reaction: Self‐healable, shape memory, and recyclable

Abstract

Covalent adaptive networks (CANs) epoxy based on the Diels‐Alder (DA) reaction usually are commonly used for self‐healing materials. However, poor toughness greatly limits its application in innovative materials. Herein, based on retaining the excellent dynamic characteristics of DA reactive CANs, we introduced thermoplastic polyurethane (TPU) in situ during crosslinking, improving the composite material's strength and toughness. A multicomponent polymeric system with advanced performance can be produced by the individual components on the condition of the synergistic hybrid effects. Molecular‐level interlocking polymer networks between the chain entanglement of TPU and the reversible covalent crosslink of DFB were formed by the topological reorganization of these two immiscible polymers. As the gelation proceeds, a homogenous structure instead of conventional phase separation is formed. When the mixing ratio of DFB and TPU is 1:1, the tensile strength of the prepared sample reaches 35 MPa, and the elongation at break reaches 110%. At the same time, the composites possess good thermal stability and solvent resistance due to the presence of interlocking polymer networks. Furthermore, these DFB‐TPU composites show excellent shape memory, self‐healing, and closed‐loop recycling properties.