Influence of solute association on the phase behavior of 12-hydroxystearic acid/n-alkane solutions.
Soft Matter
; 19(13): 2339-2349, 2023 Mar 29.
Article
en En
| MEDLINE
| ID: mdl-36876897
ABSTRACT
The phase behavior of 12-hydroxystearic acid (12-HSA) in even-numbered alkanes ranging from octane (C8) to hexatriacontane (C36) was measured by visual observation of liquid + solid to liquid and liquid-liquid to liquid cloud points and liquid + solid to liquid + liquid transitions. In general solid phases were stabilized to low concentration and higher temperature with increasing alkane length. Liquid-liquid immiscibility was observed in larger alkanes starting with octadecane. The liquidus lines of shorter alkanes (octane to hexadecane) showing only liquid to liquid + solid transitions were fit with an attenuated associated solution model based on the Flory-Huggins lattice model assuming that 12-HSA forms a carboxylic acid dimer over all concentrations investigated. The fit results show that 12-HSA forms associated structures with degrees of association ranging from 3.7-4.5 dimers in the neat 12-HSA. At low concentrations, the 12-HSA is dissociated into dimers, however the free energy cost of dissociation stabilizes the solid phase giving a sharp knee at low concentrations. The role of 12-HSA association in its phase behavior and gelation behavior are discussed. More broadly, the importance of solute association in small molecule organogelators and its potential as a molecular design parameter similar to other component thermodynamic parameters, such as melting temperature and heat of fusion, is discussed.
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1
Colección:
01-internacional
Banco de datos:
MEDLINE
Tipo de estudio:
Risk_factors_studies
Idioma:
En
Revista:
Soft Matter
Año:
2023
Tipo del documento:
Article
País de afiliación:
Estados Unidos