High-performance CNT-integrated PolyHIPE networks enabling efficient PCM encapsulation via emulsion templating for advanced thermal energy storage

One of the key approaches in passive thermal energy storage systems involves the use of structures integrated with phase change materials (PCMs), which often face challenges such as low thermal conductivity and leakage during phase transitions. In this study, a novel composite PCM was developed using a macroporous polymer framework synthesized via the high internal phase emulsion (HIPE) method. Methyl stearate (MS), with a high latent heat capacity (~280 J/g) and suitable melting point (~35 °C), was selected as the PCM. Carbon nanotubes (CNTs) were incorporated to enhance thermal conductivity and structural integrity. The resulting PolyHIPE-based composites were fabricated via vacuum-assisted impregnation, achieving 75 wt% MS encapsulation without leakage. The addition of CNTs significantly improved thermal conductivity—from 0.021 W/m·K (pristine PolyHIPE) to 0.508 W/m·K—corresponding to a 2319 % enhancement. Latent heat storage reached 209 J/g, with phase change temperatures remaining stable after 600 thermal cycles. The enthalpy reduction after cycling was <1 % (from 209.7 J/g to 209.0 J/g), indicating excellent thermal reliability. The optimized PolyHIPE@CNT/MS composite demonstrates a robust structure, high energy density, and rapid heat transfer capability, making it suitable for advanced thermal energy storage applications such as thermal management of building elements, electronic devices, Li-ion batteries, etc.