Tough Hydrogel-Mediated Constrained Assembly of Multidimensional Topological Networks for Synergistic Mechanical-Thermal Enhancement.

The rapid development of high-power flexible electronics demands thermal management materials with both high thermal conductivity and mechanical robustness. However, traditional high-loading thermal management materials suffer from an intrinsic mechanical-thermal trade-off. Herein, we propose a tough hydrogel-mediated constrained assembly strategy. By introducing carbon nanotubes (CNT) to enhance the interfacial interactions between poly(p-phenylene benzobisoxazole) (PBO) nanofibers and graphene nanosheets (GNS), a robust hydrogel intermediate is constructed. This stable intermediate unlocks the processing window for high-loading systems, allowing them to be dried into films under a 30% in-plane tensile constraint. The composite film achieves long-range orientation and extreme densification of two-dimensional (2D) nanosheets, forming a continuous multidimensional thermally conductive network via cross-scale CNT bridging. Consequently, the film exhibits a concurrent mechanical-thermal enhancement, delivering an in-plane thermal conductivity of 214 W m-1 K-1 and a tensile strength of 379.7 MPa. In practical applications, the film demonstrates outstanding bidirectional thermal management capabilities. It efficiently eliminates local hot spots in flexible electronics as a passive cooling layer and provides rapid active Joule heating to swiftly elevate the surface temperature of pouch cells. This work offers a valuable reference for next-generation flexible thermal management systems.