Phase change materials (PCMs) have received considerable attention for various latent heat storage systems for efficient thermal energy utilization. Herein, a facile and fast method for the bulk nanoencapsulation of organic PCMs is proposed, based on the thermodynamically spontaneous spreading phenomenon of three immiscible liquid phases. In this approach, a complete engulfing of PCM nanodroplets (core phase) by immiscible prepolymer droplets (coating phase), both of which are bulk-dispersed in another immiscible medium (continuous phase), is thermodynamically driven by the relation between the surface energies of the core, coating, and continuous phases. To demonstrate the proposed method, melted n-docosane (PCM, core phase) nanodroplets are completely engulfed within a couple of minutes by immiscible polyethylene glycol diacrylate (PEGDA, coating phase) in an aqueous poly(vinyl alcohol) solution (continuous phase), and the PEGDA layer quickly cross-linked upon UV irradiation to form a rigid shell protecting the PCM core. As-produced PCM nanocapsules display promising heat storage and release performances as well as high durability in repeated heating-cooling cycles in both dry and wet states. The proposed process may serve as a useful platform for bulk production of PCM nanocapsules with various core and shell compositions in a facile, fast, and scalable way.
Keywords: UV-curable prepolymer; colloidal processing; latent heat; nanoencapsulation; phase change materials; spreading; thermal energy storage.