Dynamic covalent networks and photothermal microcapsules: A synergistic strategy for autonomous repair of multi-scale defects

Microcapsule-based self-healing is an effective strategy for addressing multiscale damage in polymeric materials. However, conventional methods exhibit limited repair capabilities for large-scale damage (at the submillimeter level) under low microcapsule doping concentrations (<5 wt%). This study proposed a dual self-healing mechanism through the development of a double-shell microcapsule/modified epoxy resin composite (DMMEC). The topological reconstruction of the epoxy matrix was achieved by incorporating a 5-wt% terephthalaldehyde crosslinker, endowing the system with dynamic covalent adaptive network characteristics. Polyurethane/polyaniline (PU/PANI) double-shell microcapsules with photothermal conversion enabled infrared-triggered localized viscoelastic matrix flow, synergistically inducing damage propagation through minimal repair agent release. Notably, permittivity disparities at the microcapsule-matrix interface were found to guide the targeted development of micrometer-scale electrical tree damage, achieving efficient microscale electrical tree repair at a low doping concentration (2 wt%). Moreover, when subjected to large-scale mechanical scratch damage (2-mm length × 100-μm width), recovery rates of 91.3 % in mechanical strength and 90.4 % in electrical strength were attained. The proposed method overcomes the inherent trade-off between healing efficiency and matrix performance degradation in low-load microcapsule systems, thereby providing a novel paradigm for efficient multiscale damage restoration in polymeric materials.