Activation Energy of Crystallization for Trihydroxystearin, Stearic Acid, and 12-Hydroxystearic Acid under Nonisothermal Cooling Conditions

Abstract

The nucleation activation energy under nonisothermal cooling conditions was determined for 12-hydroxystearic acid (12HSA) (1-D crystals), stearic acid (2-D crystals), and trihydroxystearin (3-D crystals). The relative nucleation rates of trihydroxystearin and stearic acid were inversely proportional to the supercooling-time trajectory parameter (β), while 12HSA was linearly proportional to β. The differences in the proportionality to β are attributed to microscopic versus macroscopic phase separation. This suggests that both stearic acid and trihydroxystearin follow a probability density function for the number of molecules which crystallize as a function of supercooling (i.e., the greater the cooling rate, the greater the number of molecules which are incorporated into the crystal lattice). On the other hand, 12HSA molecules all crystallize when supercooled. The activation energies for stearic acid, 12HSA, trihydroxystearin, and triglycerides were 1.52, 5.40, 7.87, and 24.80 kJ/mol, respectively. The activation energy is partly affected by the polarity of the crystallizing molecules relative to the solvent. As the polarity of the crystallizing molecules increases, the activation energy decreases. However, this was not always observed because the activation energy for stearic acid was less than that of 12HSA. Therefore, the activation energy is not only a function of the molecular polarity but also due to a specific interaction between the nucleating molecules. The specific interaction affects the ability of the polar regions of the molecule to phase separate from the apolar solvent. As 12HSA and stearic acid dimerize, the carboxylic acid regions of the molecule are shielded from the solvent, but 12HSA cannot effectively shield the hydroxyl groups from the crystalline surface, resulting in a higher interfacial tension and, thus, higher activation energy.

Novel organogel based lyotropic liquid crystal physical gels for controlled delivery applications

“…At the melting point of a material, the enthalpy and the entropy of the material increases but the change in Gibb's free energy DG is zero. When the Gibb's free energy of the liquid becomes lower than the solid, melting is observed [42]. LC2 showed higher values of the change in enthalpy and entropy compared to LC1 which suggests higher thermodynamic stability of LC2 compared to LC1.…”

Thermodynamic, rheological and structural properties of edible oils structured with LMOGs: Influence of gelator and oil phase

“…The entropy change (ΔS C ) can be calculated from Eq. (1), since at the crystallization temperature the Gibb's free energy tends to zero (Lam & Rogers, 2011;Sagiri et al, 2015).…”

Hansen Solubility Parameters as a Tool in the Quest for New Edible Oleogels

“…Gelation behavior was studied experimentally using HSP for three of the most widely studied gelators: 12‐hydroxystearic acid (HSA) (Abraham et al, ; Elliger, Guadagni, & Dunlap, ; Lam & Rogers, ; Laupheimer, Preisig, & Stubenrauch, ; Rogers, Abraham, Bodondics, & Weiss, , ; Rogers & Weiss, ; Rogers, Wright, & Marangoni, , , ; Sakurai et al, ; Tachibana & Kambara, ; Terech, ; Terech, Rodriguez, Barnes, & McKenna, ), 1,3:2,4 dibenzylidene‐ d ‐sorbitol (DBS) (Grassi et al, ; Mercurio & Spontak, ; Okesola, Vieira, Cornwell, Whitelaw, & Smith, ; Shen et al, ; Stan et al, ; Xie, Rieth, & Danielson, ; Yamasaki, Ohashi, Tsutsumi, & Tsujii, ), and cholesteryl 4‐(2‐anthryloxy)butanoate (CAB) gelators (Fig. ) (Furman & Weiss, ; Terech, Furman, & Weiss, ).…”