Preparation and properties of nanoencapsulated n-octadecane phase change material with organosilica shell for thermal energy storage

Highlights: • Nanoencapsulated n-octadecane with organosilica shell was prepared in miniemulsion. • Nanocapsules with regular spherical or bowl-like morphologies were obtained. • The nanocapsules exhibit high encapsulation ratios and improved thermal stability. • The hydrophobicity of the organosilica shells can be facilely tuned. - Abstract: A novel organosilica nanoencapsulated n-octadecane phase change material was prepared through interfacial co-hydrolysis and co-polycondensation of functional silane precursors in miniemulsion. FT-IR analysis revealed that the methacryloxypropyl and methyl groups were covalently introduced into the organosilica shell materials. XRD patterns confirmed the existence and good crystallinity of n-octadecane in the organosilica nanocapsules. The organosilica nanocapsules (200–693 nm) with well-defined core–shell structure were observed by SEM and TEM. Depending on the volume ratios of silane precursors, the organosilica nanocapsules with different morphologies (bowl-like and regular spherical) were obtained. The as-prepared nanocapsules have high heat storage capability and good thermal stability, and their melting/solidifying points shift to lower temperatures due to Gibbs–Thomson effect. After 500 melting-solidifying cycles, the nanocapsules maintained their phase transition properties perfectly, indicating high thermal reliability. In addition, the hydrophobicity of the organosilica shell materials can be facilely tuned by changing the volume ratios of silane precursors.