Abstract
Phase change materials absorb the thermal energy when changing their phases (e.g., solid-to-liquid) at constant temperatures to achieve the latent heat storage. The major drawbacks such as limited thermal conductivity and leakage prevent the PCMs from wide application in desired areas. In this work, an environmentally friendly and low cost approach, layer-by-layer (LbL) assembly technique, was applied to build up ultrathin shells to encapsulate the PCMs and therefore to regulate their changes in volume when the phase change occurs. Generally, the oppositely charged strong polyelectrolytes Poly(diallyldimethylammonium chloride) (PDADMAC) and Poly(4-styrenesulfonic acid) sodium salt (PSS) were employed to fabricate multilayer shells on emulsified octadecane droplets using either bovine serum albumin (BSA) or sodium dodecyl sulfate (SDS) as surfactant. Specifically, using BSA as the surfactant, polyelectrolyte encapsulated octadecane spheres in size of ∼500 nm were obtained, with good shell integrity, high octadecane content (91.3% by mass), and good thermal stability after cycles of thermal treatments.
Highlights
The most efficient way to store thermal energy is the latent heat storage, which provides much higher storage density with a smaller temperature difference between heat storage and release [1]
We propose that the LbL assembly of Poly(diallyldimethylammonium chloride) (PDADMAC)/Poly(4-styrenesulfonic acid) sodium salt (PSS) multilayers on emulsified octadecane droplets would give the polyelectrolytePCM spheres steady entrapment and a low shell ratio of the sphere system, providing an increased latent heat storage density compared to the pure octadecane
Surfactants used in this work, bovine serum albumin (BSA) and sodium dodecyl sulfate (SDS) to be specific, were found to be able to influence the morphologies and size distributions of fabricated polyelectrolyte-phase change materials (PCMs) spheres
Summary
The most efficient way to store thermal energy is the latent heat storage, which provides much higher storage density with a smaller temperature difference between heat storage and release [1]. As a form of latent heat storage system, the large numbers of phase change materials (PCMs) melt and solidify at a wide range of temperatures, making them attractive candidates to extensive applications in varied areas such as solar energy storage, heat exchangers, and thermalregulated building strategies [1]. The most commonly used PCMs, for example, the cheap paraffin waxes (general formula CnH2n+2), are promising materials being employed for thermal-related activities because of their moderate thermal energy storage density. As a bulk material, PCM exhibits low thermal conductivity and extends to leak in the melted state; its wide application has been significantly limited [2]. In theory, encapsulated PCM materials as micro/nanoparticles could reduce their reactivity towards the outside environments, generate larger heat transfer surface, and most importantly could govern their changes in volume as thermal-related phase change occurs
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