Lignin–Polyethylene Oxide Interlocked Phase Change Materials with Enhanced Thermal Stability and Form Retention for Efficient Heat Management

The rapid advancement of high-performance technologies, such as electric vehicle (EV) batteries; data centers; and AI systems, has underscored the critical need for effective thermal management solutions. Conventional phase change materials (PCMs) often face challenges, like phase leakage, dimensional instability, and environmental concerns, limiting their effectiveness in high-stress applications. This study introduces a novel PCM composed of polyethylene oxide (PEO) and lignin, developed to overcome the existing limitations while improving overall thermal management performance and promoting material sustainability. By chemically crosslinking lignin with aliphatic polymer chains compatible with PEO during co-reactive melt processing, we created an interlocked structure that combines high heat capacity with exceptional structural stability. This structure allows the PCM to retain its form and resist phase transitions even under elevated temperatures, up to 115 °C, far above the melting point of PEO, effectively mitigating leakage issues common in conventional PCMs. Comprehensive thermal characterization and dynamic performance testing demonstrate that the lignin-modified PEO composites effectively absorb and dissipate heat, maintaining dimensional stability and resilience under repeated thermal cycling. These findings position these composites as sustainable, reworkable, and efficient alternatives for advanced thermal management applications, particularly in battery thermal management systems (BTMSs), where stability, durability, and performance are critical.