Supramolecular liquid metal-composites: A new class of multiphase soft materials

The advancement of polymer science for next-generation applications in flexible electronics, soft robotics, and bio-integrated devices requires innovative strategies to achieve metallic conductivity while maintaining the inherent softness and elasticity of elastomeric networks. Traditionally, the development of conductive polymer composites has relied on rigid, solid fillers, leading to a detrimental trade-off: enhanced conductivity often compromises processability and mechanical properties, such as reduced stretchability and toughness. This review presents a paradigm shift in the design of polymer composites through the precise control of liquid metals (LM) as fluidic metallic inclusion via supramolecular interfacial engineering. This strategy creates a new class of supramolecular LM-composites that effectively decouple electrical performance from mechanical toughness, addressing a long-standing challenge in the field. We analyze the resulting physicochemical properties, establishing crucial structure-property relationships for this novel class of polymer composites. The key to unlocking the potential of these systems lies in supramolecular polymer engineering, which includes unique soft matter mechanics, stable electromechanical performance, and stimuli-responsive properties. Furthermore, we survey how these highly functional polymer composites are being leveraged in advanced devices. Ultimately, this review synthesizes the state-of-the-art and establishes clear design principles, positioning supramolecular LM-polymer systems not merely as functional materials but as a frontier for advancing polymer chemistry and physics.