Tough and body-temperature self-healing polysiloxane elastomers through building a double physical crosslinking network via competing non-covalent interactions

Abstract

Polydimethylsiloxane (PDMS)-based elastomers with superior mechanical and body-temperature self-healing properties might find attractive applications in wearable electronic devices. Herein, we propose a new design strategy by creating a double physical crosslinking network that contains at least three competitive interactions to achieve a tough and body-temperature self-healing elastomer. First, a urea-containing PDMS (PDMS-U) was synthesized through a chain extending reaction between bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (H₂N-PDMS-NH₂) and 2,4′-tolylene diisocyanate (TDI). The introduction of urea groups was designed to offer hydrogen bonding and urea/metal ion coordination interactions. Second, a carboxylic acid (COOH) functionalized PDMS (PDMS-C) was synthesized via post-modification of the vinyl containing PDMS precursor. The introduction of COOH was aimed at forming COO⁻/metal ion coordination bonds. Finally, mixing PDMS-U and PMDS-C with different metal ions could create PDMS elastomers with a dual network arising from three competitive interactions, i.e., hydrogen bonding of ureas, and urea/metal ion and COO⁻/metal ion coordination interactions. Among these elastomers, the PDMS-U/PDMS-C_0.3/Zn²⁺ composite shows the best comprehensive properties, of which tensile strength, breaking strain, and toughness are as high as 4.0 MPa, 776%, and 16.0 MJ m⁻³, respectively. In addition, its self-healing efficiency at body temperature can reach up to 98%. The robust self-healing elastomer can be used as a flexible substrate to easily fabricate healable electrodes.