Structural and thermal properties of unpurified and purified 12-hydroxystearic acid solutions

Abstract

We investigated the effect of impurities on gel properties of 12-hydroxystearic acid (12-HSA) in organic solvents by means of differential scanning calorimetry (DSC), small-angle and wide-angle X-ray scattering (SAXS and WAXS). The melting and crystallization behaviors of unpurified 12-HSA powder are quite different from those of purified 12-HSA powder. The former melting point is by 2.9 °C lower than that of purified 12-HSA and the endothermic peak is very broad because of existence of impurities. On the other hand, the melting and crystallization behaviors of unpurified 12-HSA gel are slightly different from those of purified 12-HSA gels. The SAXS experiments reveal that the fiber structure of unpurified 12-HSA gel is similar to that of purified 12-HSA gel. For the 12-HSA gel in toluene which forms transparent gel, the cross-sectional size of the fiber estimated to be 110 Å for both purified gels and unpurified gels. These results suggest that gel properties of 12-HSA solutions are relatively insensitive to existence of impurities.