Synergistic polymer-gelator design enables formation of stable phase change materials

The shift from fossil-derived paraffins to renewable alternatives is critical for sustainable energy and climate-change mitigation. Bio-based phase change materials (PCMs), such as fatty acid esters, are promising, yet their adoption is limited by severe leakage at high loadings. Here, we introduce a modular stabilization strategy for dimethyl ester PCMs using poly(l-lactic acid) (PLLA) and sorbitol-derived organogelators through thermally induced phase separation. PLLA scaffolds provide weak shape stability and limited liquid retention (40% leakage). Covalently linked PLLA-gelator hybrid structures with excess gelator form robust, hierarchical scaffolds that reduce leakage to 7% while preserving a high latent heat (140 J g-1). The leakage and performance are directly connected to the microstructure of the scaffolds. By combining thermal buffering and recyclability, these PCMs pave the way for sustainable, bio-based materials in thermal energy storage.