Flexible rubber with metal-like thermal conductivity achieved via hydrogen bonding engineering

The ideal electronics packaging for next-generation wearable devices and integrated circuits would be a flexible material with high thermal conductivity of a metal. We report a liquid-metal polyurethane composite (LiMPuC) with a thermal conductivity of 23.42 W m-1 K-1 while retaining extreme stretchability. The performance arises from interfacial-chemistry-guided ordering of the polyurethane matrix and improved liquid-metal wetting. By modulating hydrogen-bond donor/acceptor densities in the thermoplastic polyurethane and grafting –NH2 groups onto eutectic gallium–indium (EGaIn) droplets, we create anchored, reconfigurable interfaces that (i) increase matrix chain alignment and intrinsic heat transport and (ii) promote stable, strain-tolerant thermal near-percolation of the liquid metal. Under large tensile strain, these coupled effects preserve high conductivity and deliver a flexibility figure of merit > 100. This chemistry-to-microstructure pathway, linking hydrogen-bond engineering with LM surface functionalization, provides a general strategy for designing flexible, high-$$\kappa$$ composites for advanced thermal management in emerging electronics. Liquid metals can create flexible, conductive composites, but often show a trade-off between these properties. Here, the authors optimise the interactions between liquid-metal and polyurethane to obtain a composite with high thermal conductivity and stretchability at low liquid metal loading.