MD-guided nucleation agent development for supercooling control in fatty alcohol PCM emulsions

Abstract

Supercooling in phase change dispersions significantly undermines the benefits of high latent heat storage capacity, especially those utilizing paraffin-based phase change materials (PCMs) because the delay in crystallization below the thermodynamic freezing point reduces both energy efficiency and system reliability due to the stochastic nature of nucleation. This work leverages Molecular Dynamics simulations with the OPLS force field to identify and design nucleation agents that mitigate supercooling by closely matching the structural and chemical characteristics of the PCM. Initial reference simulations over 100 ns of the PCM 1-docosanol showed crystallization onset at 320 K (47°C), 23 K below the bulk melting point, which was used to evaluate a range of candidate seed materials at 4–8 wt% loading, including higher-melting homologues and tailored ether-based dimers. The simulations revealed that optimal nucleation occurs when the seed offers a surface structurally analogous to the PCM’s molecular arrangement, promoting lateral crystalline growth and minimizing orientation barriers. Surfactant molecules with structurally compatible tail (e.g., C22 vs. C12) further reduced supercooling by 10 K. Subtle factors, such as consistent numbers of carbon atoms, were also found to influence crystallization behavior.

Experimental validation confirmed the simulation predictions, as a newly designed ether-based seed increased the onset crystallization temperature by additional 0.7 ± 0.1 K (≈10 %) compared to established nucleation additives. By guiding seed design through simulations, the approach lowers the need for extensive trial-and-error experiments, accelerating the development of improved nucleation additives. Overall, this study provides insights into the molecular mechanisms of PCM crystallization, offering a pathway to more efficient thermal energy storage systems through rational, simulation-informed material selection.