Understanding the microstructure of emulsions is indispensable for further improvements of cosmetic formulations. In the present study, we describe the application of a field-emission scanning electron microscope that incorporates a cryo-system (cryo-FESEM) to achieve high resolution, therefore enabling the characterization of the microstructures of emulsions. The emulsions used in this study were oil-in-water types composed of surfactant-cetostearyl alcohol-water system. To prepare a flat cross section of the emulsion specimen with good reproducibility, a cryomicrotome was adopted after rapidly freezing the emulsion with slush nitrogen. The cryo-FESEM images revealed clearly that the emulsion was formed of spherical lamellae with concentric circles. Thus we confirmed that the preparation of cross sections of frozen specimens with the cryomicrotome and their observation by the cryo-FESEM were useful to clarify the microstructures of emulsions. This methodology will be able to contribute both to understand the relation between microstructures and rheology of emulsions and to design novel emulsions for cosmetic products.
Journal of Japan Cosmetic Chemists Association