Liquid Crystal Make-up Remover. Conditions of Formation and its Cleansing Mechanisms.

Abstract

Synopsis Oily residues of make-up cosmetics tend to remain in the sulcus cutis and pores of the skin. In order to remove them without causing skin irritation, two particular properties are required: 1) immediate dissolution and/or dispersion of remaining cosmetics with a make-up remover, and 2) the facility of rinsing off the remover containing the residual cosmetics from skin. In order to meet the former need, the remover must be lipophilic, and for the latter, it must be hydrophilic. Therefore, two opposite properties are required in one product. We have been able to overcome this problem by using a lyotropic liquid crystal system. A liquid crystal that consists of a branched alkyl surfactant and a polyol is able to contain a large amount of oil. As it is bicontinuous to both oil and water phases, the oil-based cosmetics can be dissolved and dispersed easily by rubbing skin with the remover. During the rubbing process, a phase transition occurs, thus enhancing the dissolution of the oily impurities due to the disruption of the liquid crystal structure. In the rinsing process, the oil phase that dissolves the oily residues can be removed from the skin by self-emulsification. The sequential cleansing mechanism of rinsing process is 1) reformation, by addition of water, of a lamellar liquid crystal (LC) containing the oily residues, 2) phase transitions: LC-> O/LC-> O/W emulsion, and 3) removal of the emulsion. During these processes, the interfacial tension between oil and water phases becomes very low and forms fine emulsion droplets, which means they can be rinsed off very easily with the dispersion force of Brownian movement.