Configurable Nature‐Derived Phase‐Change Nanocapsules From Chitosan‐Stabilized Emulsions of Ternary Deep Eutectic Solvent

ABSTRACT Phase‐change materials (PCMs) offer an appealing strategy for passive thermal energy storage, but conventional PCMs often suffer from limitations in thermal performance, supercooling, and structural stability. Herein, we engineered adjustable PCM nanocapsules deploying a novel ternary deep eutectic solvent (DES) system composed of capric acid, palmitic acid, and octadecane. The DES formulation exhibited a notably high latent heat of fusion of 225.1 J/g and phase‐transition temperatures precisely tuned to the human comfort range ( T m = 23.5°C, T f = 22.6°C), surpassing many previously reported DESs (typically ≤ 207.2 J/g). The optimized DES was further encapsulated within a cross‐linked chitosan shell to create nanocapsules with an average size of 240 nm with a high encapsulation efficiency (> 92%). These nanocapsules retained a latent heat of 207.0 J/g, among the highest reported for encapsulated PCMs, and exhibited exceptional thermal cycling stability over 100 heating/cooling cycles, with negligible phase‐transition temperature shift and no observable leakage. Structural analyses confirmed successful DES encapsulation and uniform shell formation. The superior thermal storage capacity, structural integrity, and sustainability of the developed PCM nanocapsules establish them as strong candidates for next‐generation smart thermal management systems in buildings and other advanced applications.