Synthesis of Uniform Alkane-Filled Capsules with a High Under-Cooling Performance and Their Real-Time Optical Properties.

Encapsulating under-cooling materials has been a promising strategy to address the compatibility issue with a surrounding matrix. Herein, we present the synthesis of a uniform alkane-infilled capsule system that shows obvious under-cooling properties. As demonstrating examples, n-hexadecane was selected as a liquid alkane and n-eicosane as a solid in our systems as core materials via in-situ polymerization, respectively. The under-cooling properties of capsules were investigated using differential scanning calorimetry, real-time optical observations with two polarizers, and molecular modeling. The n-hexadecane encapsulated capsules exhibited a large under-cooling temperature range of 20 °C between melt and crystallization, indicating potential applications for structure-transformation energy storage. In addition, molecular modeling calculations confirmed that the solid forms of n-hexadecane and n-eicosane are more stable than their liquid forms. From liquid to solid form, the n-hexadecane and n-eicosane release energies were 4.63 × 10³ and 4.95 × 10³ J·g-1, respectively.