Clusters in Liquid Fatty Acids: Structure and Role in Nucleation

Area of Science:

• Materials Science
• Physical Chemistry
• Chemical Engineering

Background:

• Saturated fatty acids are utilized in consumer products and show potential as phase change materials for thermal energy storage.
• Their ability to crystallize with minimal supercooling is advantageous, but this property is linked to molecular clustering in the liquid phase.
• Understanding these clusters is key to optimizing their performance in thermal energy storage applications.

Purpose of the Study:

• To investigate the size, structure, and temperature-dependent behavior of molecular clusters in saturated fatty acids.
• To elucidate the relationship between these clusters and the phenomenon of supercooling.
• To quantify the impact of these clusters on the crystallization process and energy storage capabilities.

Main Methods:

• Raman spectroscopy
• Density functional theory (DFT) calculations
• Small-angle X-ray scattering (SAXS)

Main Results:

• Liquid fatty acids exhibit ordering at all temperatures, with molecules showing short-range alignment.
• Below a critical temperature, large clusters (hundreds of molecules) of ordered fatty acid dimers form, featuring interdigitated alkyl chains.
• Above this temperature, clusters are smaller and less numerous, impacting supercooling susceptibility.

Conclusions:

• Fatty acid clusters play a crucial role in promoting bulk crystallization by reducing the energy barrier for crystal growth.
• The observed temperature-dependent cluster dynamics explain the supercooling behavior of saturated fatty acids.
• These findings provide insights for designing improved phase change materials for thermal energy storage.