Rheology Control Agents for Cosmetics

Abstract

"Usage feeling" is one of the most important characteristics of cosmetics, particularly skin-care products. Because the usage feeling of cosmetics is strongly related to their rheological properties, the ingredients, which affect the rheological properties of the product, are key factors in the development of skin-care products. In this chapter, two types of novel rheology control agents for cosmetics that have been developed are described. The first is hydrophobically ethoxylated urethane, which contains a relatively large C24 hydrophobe. This telechelic polymer forms a transient network structure in aqueous systems. Because the transient network structure is due to physical interactions, it is easily destroyed and reconstructed. This interesting physical property creates a unique usage feeling for use in skin-care products. The second agent is a water-swellable microgel that was polymerized in a W/O microemulsion system. Although water-soluble polymers are widely used in cosmetics as viscosity thickeners, the thickeners often suffer a serious problem, so-called spinability, which is due to the entanglement of polymer chains. In contrast, microgels avoid such problems. The details of these rheology control agents, their syntheses, physicochemical properties, and rheological properties are reviewed.