Room-Temperature Dynamic and Creep-Resistant Covalent Adaptive Networks via Phase-Locked Benzimidazole Urea Bonds: Toward Recyclable Elastomers for Wearable Electronic Devices

The rapid development of flexible electronic devices has resulted in serious electronic pollution, which has aroused great attention in recent years. This study focuses on the development of dynamic cross-linking poly(dimethylsiloxane) (PDMS) elastomers with covalent adaptive network structures that can be recycled by a solvolytic approach to address this challenge. The elastomer is prepared through the addition reaction between amine-terminated PDMS, isophorone diisocyanate, and 2-aminobenzimidazole followed by cross-linking with hexamethylene diisocyanate trimer. The secondary ureidobenzimidazole (SUBI) moieties formed by benzimidazole and isocyanate groups can undergo a six-membered-ring transition state, enabling automatic dissociation and reformation character at room temperature. Hydrogen-bonded aggregates formed by SUBI moieties work as physical cross-linking units to protect urea bonds from dissociation, which endows the materials with excellent creep-resistant performance. Decomposition of the aggregates by solvation, releasing the SUBI moieties, is mainly responsible for the recycling process. Wearable electronic devices with a microcrack structure for vibratory monitoring are assembled through 3D printing nanosilver paste onto the elastomer with predesigned structure. The excellent recycling performance can be transferred from the PDMS substrate to the devices, which enables the separation of PDMS and nanosilver, providing promising principles to develop facile degradable materials at room temperature for fabricating recyclable wearable electronic devices.