Covalently Interconnected BN/CNTs Hybrid Networks Enhance the Thermal Conductivity and Electrical Insulation of Phase Change Composites for Advanced Thermal Management

Achieving efficient thermal management in high-power and flexible electronic devices remains a major challenge, particularly in the development of polymer-based phase change materials (PPCMs). Here, we report a PPCMs constructed by embedding covalently bonded boron nitride/carbon nanotubes (BN/CNTs) hybrids into a paraffin wax/ polydimethylsiloxane (PW/PDMS) matrix, which is called PW/PDMS@BN/CNTs (PPBC). The hybrids were synthesized through dopamine-assisted polymerization and amidation between amino-functionalized BN and carboxylated CNTs, forming continuous, chemically connected heat transfer networks. Structural analyses confirm stable amide linkages and homogeneous dispersion of fillers. The optimized PPBC exhibits a maximum thermal conductivity of 5.92 W·m −1 ·K −1 and a maximum latent heat of 92.5 J·g −1 . It also shows excellent cycling stability and leakage resistance with < 2% mass loss after 100 cycles. Thermal management tests reveal that PPBC coatings reduce operating temperatures of lithium-ion batteries and light-emitting diode (LED) chips by 10°C–30°C, achieving uniform heat dissipation and long-term reliability. In active modes, PPBC films deliver solar-thermal and electro-thermal conversion efficiencies exceeding 80%, remaining stable over 50 cycles. This work offers a generalizable strategy for designing flexible, high-performance, and electrically insulating PPCMs for advanced thermal management applications.