Tough non-covalent adaptable networks: Cation-π cross-linked rigid epoxy

Polymeric materials containing dynamic crosslinks and adaptable networks have obscured the line between the “thermosets” and “thermoplastics”, since they are able to be reprocessed or welded while being permanently cross-linked at the same time. However, it is still a great challenge to combine the good mechanical properties and excellent dynamic properties. Herein, cation-π interactions between indole groups and Eu3+ were applied as cross-links in rigid networks of thermosetting epoxy to form tough non-covalent adaptable networks (NANs). The cation-π cross-linked epoxy exhibited outstanding solvent resistance and excellent mechanical properties with the tensile strength of 38 MPa, while the glass transition temperature (Tg) was up to 87 °C. Moreover, the cross-linked epoxy could be readily reprocessed and welded at moderate temperature of 120 °C, while the tensile strength recovered to 32 MPa after recycling. Meanwhile, the epoxy exhibited other dynamic properties including triple shape memory and tension triggered fluorescence. The readily prepared cation-π cross-linked epoxy provides a general way to develop tough NANs with high performance and excellent dynamic properties, which may be suitable for other non-covalent dynamic bonds and thermosetting matrix.