Clusters in Liquid Fatty Acids: Structure and Role in Nucleation
| Autor: | John A. Noël, Luc M. LeBlanc, Mary Anne White, Laurent Kreplak, Michael D. Fleischauer, Erin R. Johnson, Daphne Sunita Patterson |
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| Rok vydání: | 2019 |
| Předmět: |
Nucleation
Crystal growth 02 engineering and technology 010402 general chemistry 01 natural sciences 7. Clean energy law.invention symbols.namesake FIB law Materials Chemistry Physics::Chemical Physics Physical and Theoretical Chemistry Crystallization Supercooling water membrane Alkyl star block copolymer chemistry.chemical_classification Quantitative Biology::Biomolecules antifouling coating Fatty acid 021001 nanoscience & nanotechnology HT-TEM 0104 chemical sciences Surfaces Coatings and Films chemistry 13. Climate action Chemical physics SEM TEM symbols HT-AFM Density functional theory AFM 0210 nano-technology Raman spectroscopy |
| Zdroj: | The Journal of Physical Chemistry B. 123:7043-7054 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/acs.jpcb.9b05017 |
| Popis: | Saturated fatty acids are used in many consumer products and have considerable promise as phase change materials for thermal energy storage, in part because they crystallize with minimal supercooling. The latter property correlates with the existence of molecular clusters in the liquid; when heated above a threshold temperature, clusters do not immediately re-form on cooling, and supercooling results. Raman spectroscopy, density functional theory calculations, and small-angle X-ray scattering were used to reveal the size, structure, and temperature dependence of the clusters. We found that the liquid phases of fatty acids contain some ordering at all temperatures, with the molecules showing, on average, short-range alignment along their long axes. At temperatures below the threshold temperature for increased susceptibility to supercooling, clusters of more highly ordered fatty acid dimers, several hundred molecules in size, exist in the liquid. Within these clusters, the alkyl chains of the fatty acid dimers are essentially completely inserted between the alkyl chains of their longitudinal neighbors. Above the threshold temperature, fatty acid clusters are smaller in size and number. We explored how the fatty acid clusters promote bulk crystallization and show quantitatively that their presence reduces the energy barrier to crystal growth, likely by a particle-attachment-type mechanism. |
| Databáze: | OpenAIRE |
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