10.1021/acs.jpcb.8b10568.s001
John A. Noël
John A.
Noël
Laurent Kreplak
Laurent
Kreplak
Nuwansiri Nirosh Getangama
Nuwansiri Nirosh
Getangama
John R. de Bruyn
John
R. de Bruyn
Mary Anne White
Mary Anne
White
Supercooling and Nucleation of Fatty Acids: Influence
of Thermal History on the Behavior of the Liquid Phase
American Chemical Society
2018
Fatty Acids
alkyl chains
material-dependent threshold temperature
PCM
supercooling threshold temperature
Thermal History
consumer products
phase change materials
acid supercooling
acid molecules
supercooling results
temperature show
threshold temperature
Liquid Phase
energy storage
NMR T 1 hysteresis
acid nucleation
acids increases
2018-12-03 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Supercooling_and_Nucleation_of_Fatty_Acids_Influence_of_Thermal_History_on_the_Behavior_of_the_Liquid_Phase/7464791
Saturated
fatty acids are an exceptionally important class of liquids,
used in many consumer products and suggested as phase change materials
(PCMs) for thermal energy storage, in part because they crystallize
with minimal supercooling. Here we investigate fatty acid nucleation
to understand why crystallization is so facile, as a step toward identifying
potential mechanisms for the suppression of supercooling in other
PCMs. We find that fatty acid supercooling can be induced only if
the liquid is first heated above a material-dependent threshold temperature.
NMR spin–lattice relaxation time studies show that the average
mobility of the alkyl chains in the fatty acids increases more rapidly
with temperature above the supercooling threshold temperature, and
NMR <i>T</i><sub>1</sub> hysteresis also sets in at that
temperature. Measurements of the real portion of the dielectric constant
as a function of temperature show that a liquid fatty acid heated
far above its melting point behaves with an apparent temperature upon
cooling that is higher than the actual temperature, when compared
to its behavior at the same temperature upon heating. Our results
suggest that molecular clusters in the liquid fatty acids break apart
when the liquids are heated above their threshold temperature and
do not immediately re-form on cooling. The breakup of clusters leads
to an increase in the mobility of the fatty acid molecules. Because
the clusters do not re-form quickly on subsequent cooling, nucleation
does not occur, and substantial supercooling results.