A Leakage-Free Solid–Solid Phase Change Composite with High Thermal Conductivity and EMI Enabled by Covalent Functionalization and a Quasi-Hyperbolic Framework

With the rapid advancement of artificial intelligence, smart sensing technologies, and batteries with high power density, thermal management has become a critical issue for electronic devices. Phase change materials (PCMs) offer promising applications in thermal management. However, it is a significant challenge to fabricate PCMs with high thermal conductivity (TC) and electromagnetic interference shielding effectiveness (EMI SE) while maintaining a leakage-free performance. This work reports leakage-free solid–solid phase change composites with high TC and EMI SE enabled by covalent functionalization and a quasi-hyperbolic framework. The solid–solid phase change material (OP) is synthesized via a nucleophilic ring-opening reaction of epoxy groups, where octadecanol (OD) is grafted onto the side chains of polyethylene-co-methyl acrylate-co-glycidyl methacrylate (PEMAGMA). Subsequently, it is filled into the electrochemically expanded graphite (EEG) framework through vacuum filtration, in which the EEG framework is produced using an electrochemical expansion method and has high TC and EMI SE. The obtained OP/EEG composites exhibited excellent properties, including very low leakage (0.6%), high latent heat (86.45 J/g), ultrahigh TC (22.6 W/(m·K)), and superior EMI SE (110.28 dB). This material shows great potential for improving the heat transfer efficiency of thermal interface materials (TIMs) in practical applications, demonstrating a promising outlook in the field of thermal management.