Abstract
This work deals with the investigation of the polymorphic changes associated with stearic acid in the presence of Tween 20 during the formation of oleogels. Tween 20 was utilized as a crystal habit modifier and its effect on the physical and thermal properties of the oleogels have been studied. Tween 20 was found to stabilize the polymorph B of stearic acid, marked by an increase in the leaf-like structures. Fluorescent recovery after photobleaching studies suggested Tween 20 concentration-dependent reduction in the mobile fractions. Gelation studies suggested a delay in the induction time of nucleation of stearic acid in the presence of Tween 20 was due to the decrease in the degree of supercooling. Avrami analysis supported the stabilization of the polymorph B of stearic acid in the presence of Tween 20. XRD measurements indicated that Tween 20 promoted the growth of the stearic acid crystals while forming leaf-like structures. The molecular rearrangement of the gelator network was quicker and ordered in the Tween 20-containing oleogels. The increase in ordered arrangement of the stearic acid molecules has lowered the crystal imperfections. In other words, it enhanced the crystal gaps (pores) associated with the gelators. When stress (either thermal or mechanical) was introduced, the strength of the oleogels was decreased due to the syneresis of oil through the pores. An increase in the Tween 20 concentration-dependent relaxation of the oleogels was also observed due to the polymorphic change and arrangement of the gelators.