Dual-crosslinking side chains with an asymmetric chain structure: a facile pathway to a robust, self-healable, and re-dissolvable polysiloxane elastomer for recyclable flexible devices

Abstract

The facile fabrication of robust, self-healable, and re-dissolvable polysiloxane elastomers for use in recyclable flexible devices is highly desired yet quite a challenge. Herein, a strategy involving dual-crosslinking side chains with an asymmetric chain structure is proposed to overcome the related challenges. Dual crosslinking is readily undergone between diethylenetriamine-functionalized polysiloxane (PDETAS) as the matrix and 4-formylbenzoic acid (FBA) as the crosslinker. Besides traditional crosslinking between diethylenetriamine side-chain terminals at 25 °C, further crosslinking occurs involving the middle of side chains at 100 °C. More importantly, the formed crosslinked chains have an asymmetric structure, where one type of crosslinking involves strong covalent imine or aminal bonds that maintain the structure stability, while the other involves weak noncovalent ionic hydrogen bonds that endow the material with re-dissolvability. The robust elastomer with tensile strength of 12 MPa can repeatedly recover from damage when it is healed at 100 °C for 2 h. The crosslinked elastomer can be redissolved without any extra additives, and the regenerated elastomer exhibits similar tensile strength to its pristine form. The elastomer also has excellent adhesion strength (∼8 MPa), similar to some commercial adhesives, and the adhesion is recoverable after three bonding and debonding cycles. Moreover, a flexible carbon nanotube/elastomer composite reveals excellent strain sensitivity, and more than 90 wt% of the carbon nanotubes and matrix can be recycled from the composite after it is re-dissolved at 80 °C for 2 h. This study indicates a simple but effective concept for obtaining a robust, self-healable, and re-dissolvable polysiloxane elastomer that exhibits application potential in recyclable flexible devices and adhesives.