Nanostructure of Cosmetics: Characterization and Correlation with Macroscopic Properties

Understanding the nanostructure of cosmetic products can help predict their macroscopic and sensory properties. However, in this industry, there is a significant gap in knowledge regarding the physical chemistry of colloids, which limits the actuation of many professionals. This study aims to develop a classification of cosmetics as colloidal systems by characterizing products representative of different colloid categories and correlating their classes and structures with rheological and textural properties. To this end, a survey of commercial and chemical data from different cosmetics was conducted, followed by an analysis of the products using techniques such as microscopy, laser diffraction, texturometry, and rheology. These results were used to identify the colloidal class of different products, such as micellar solutions, liquid crystals, emulsions, foams, suspensions, gels, or aerosols. Additionally, properties such as the hydrodynamic radius of micelles, the size, and morphology of drops, particles, and bubbles, viscosity, spreadability, penetration, and stability were determined. In this way, classifying cosmetics as colloids and characterizing them will provide a better understanding and greater control over how the macroscopic properties of cosmetics derive directly from their colloidal structures, helping formulators achieve more precise control over the properties of the formulations developed.