Interface-Encoded Dynamic Covalent Crosslinking Enables Ultra-Stretchable, Signal-Stable Conductive Elastomers

Conductive composite elastomers for soft electronics are often constrained by a fundamental trade-off: weak filler-matrix adhesion leads to interfacial defects, stress concentration, and signal instability under dynamic strain, whereas conventional covalent "locking" improves adhesion at the cost of elasticity and stretchability. Here, we report a dynamic covalent interface engineering strategy that resolves this conflict by converting the filler-matrix boundary into a reconfigurable, stress-dissipative covalent junction. Lipoic-acid-functionalized carbon nanofibers (CNFs) serve as nanoscale multi-point crosslinkers within a polylipoic-acid-based elastomer, where surface-grafted 1,2-dithiolane rings undergo reversible disulfide exchange with the matrix to strengthen stress transfer while preserving network mobility. The resulting bio-based conductive elastomers exhibit ultra-stretchability (∼4200%) with markedly enhanced toughness and up to three- to fivefold higher conductivity compared with unmodified-CNF controls. They operate over an exceptionally wide sensing range (0%-3000% strain), delivering gauge factors up to 8.13 and ∼2× higher ΔR/R₀ amplitudes, together with highly reproducible, low-hysteresis responses under repeated large-strain deformation. DFT calculations support the interfacial mechanism by revealing strengthened disulfide-mediated binding. Enabled by the same dynamic chemistry, the elastomers further show room-temperature self-healing and closed-loop recyclability. This work establishes an interface-encoded molecular design principle for ultra-stretchable, electromechanically stable, and sustainable conductive elastomers.