Dual Dynamic Cross-Linked Epoxy Vitrimers Used for Strong, Detachable, and Reworkable Adhesives

Abstract

Novel reprocessable thermosetting adhesives (RTAs), which combine high adhesive strength, reusability, disassembly, and recyclability features, have attracted increasing attention. However, developing RTAs with a rapidly adhesive rate while ensuring high adhesive strength and self-healing ability is still a significant challenge. Here, we prepared a novel vitrimer called DA<i>x</i>-DTSA<i>y</i>, which can be used as an RTA. First, by adjusting the ratio of rigid and flexible segments, maximum tensile strength reached 35.92 MPa. Second, the combined effect of dynamic hydroxyl ester bonds and dynamic disulfide bonds resulted in a rapid stress relaxation behavior, with a complete relaxation time 13.6 times shorter than a vitrimer only cross-linked with hydroxy ester bonds. This feature endowed its good self-healing and reprocessing capabilities. After self-healing at 180 °C, the maximum healing rate of mechanical properties was 91.8%. After three reprocesses, the maximum recovery rate of tensile strength was 120.2%. Furthermore, the combination of rigid and flexible segments and the synergistic effect of dual dynamic covalent bonds made DA<i>x</i>-DTSA<i>y</i> capable of use as a high-performance RTA. The lap shear strength of a DA<i>x</i>-DTSA<i>y</i> film on stainless steel reached 18.18 MPa after 15 min, with a recovery rate of 91.9% after 5 rebonding cycles. Additionally, DA<i>x</i>-DTSA<i>y</i> can be disassembled in chemical agents and exhibited better insulation properties compared to traditional epoxy resins. DA<i>x</i>-DTSA<i>y</i> can be employed as a novel high-performance adhesive in applications such as electronic devices and transportation, contributing to the development of thermosetting adhesives toward recyclability and sustainability.