Covalently Functionalized Leakage‐Free Healable Phase‐Change Interface Materials with Extraordinary High‐Thermal Conductivity and Low‐Thermal Resistance

Abstract Phase‐change materials (PCMs) have received considerable attention to take advantage of both pad‐type and grease‐type thermal interface materials (TIMs). However, the critical drawbacks of leaking, non‐recyclability, and low thermal conductivity (κ) hinder industrial applications of PCM TIMs. Here, leakage‐free healable PCM TIMs with extraordinarily high κ and low total thermal resistance (R_t) are reported. The matrix material (OP) is synthesized by covalently functionalizing octadecanol PCM with polyethylene‐co‐methyl acrylate‐co‐glycidyl methacrylate polymer through the nucleophilic epoxy ring opening reaction. The OP changes from semicrystalline to amorphous above the phase‐transition temperature, preventing leaking. The hydrogen‐bond‐forming functional groups in OP enable nearly perfect healing efficiencies in tensile strength (99.7%), κ (97.0%), and R_t (97.4%). Elaborately designed thermally conductive fillers, silver flakes and multiwalled carbon nanotubes decorated with silver nanoparticles (nAgMWNTs), are additionally introduced in the OP matrix (OP‐Ag‐nAgMWNT). The nAgMWNTs bridge silver‐flake islands, resulting in extraordinarily high κ (43.4 W m⁻¹ K⁻¹) and low R_t (30.5 mm² K W⁻¹) compared with PCM TIMs in the literature. Excellent heat dissipation and recycling demonstration of the OP‐Ag‐nAgMWNT is also carried out using a computer graphic processing unit. The OP‐Ag‐nAgMWNT is a promising future TIM for thermal management of mechanical and electrical devices.