Microencapsulation of phase change materials via nanopolysaccharide complex-stabilized Pickering emulsions

Microencapsulation of phase change materials (PCMs) within polymer shells is an effective approach to prevent leakage, improve thermal conductivity, and broaden their applications in thermal energy storage. Herein, the fully bio-based complex of lignin-containing cellulose nanofibrils (LCNF) and chitin nanofibers (ChNF) was tailored to stabilize Pickering emulsion for in-situ polymerization of PCM microcapsules with a melamine-formaldehyde (MF) resin shell. The droplet size and stability of the emulsions can be effectively controlled by adjusting the morphology difference and concentration of the oppositely charged LCNF (negatively charged) and ChNF (positively charged). An optimal LCNF/ChNF complex stabilization system (LCNF: ChNF = 0.25 wt%: 0.25 wt%) was identified and utilized to stabilize n-octadecane (C₁₈) Pickering emulsions, thereby forming the basis for high-performance PCM microcapsules. The resulting microcapsules exhibited excellent thermal properties, including outstanding thermal cycling stability and a high latent heat storage capacity exceeding 205 J/g. Furthermore, the MF polymer shell provided microcapsules with a high encapsulation rate and encapsulation efficiency of 84.5% and 99.8%, respectively, while ensuring no leakage under prolonged high-temperature conditions. These results highlight the potential of the LCNF/ChNF complex as a green and effective stabilizer for PCM microcapsules, offering a new insight into sustainable solutions for energy storage technologies.