SOLID LIPOSPHERES OBTAINED FROM HOT MICROEMULSIONS IN THE PRESENCE OF DIFFERENT CONCENTRATIONS OF COSURFACTANT - THE CRYSTALLIZATION OF STEARIC-ACID POLYMORPHS

Solid lipospheres were obtained from a series of six microemulsions prepared at about 70-degrees-C, containing increasing concentrations of butanol and fixed levels of stearic acid, Tween 20 and water. The lipospheres, obtained by dispersion of the microemulsions in cold water, were analysed by X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) in order to examine the influence of butanol on the crystal polymorphs of stearic acid. Polymorph B, present in three samples, is favoured in the presence of a small amount of butanol. In contrast, polymorph B is not present in mixtures of stearic acid, butanol and Tween 20, which had undergone the same thermal cycle and had the same composition as the above liposphere samples. Therefore, the droplet microemulsion structure allowed the formation of polymorph B, within the concentration limits of butanol deduced in this study.