Surface Morphology of Cosmetic Film Consisting of PEG-Diisostearate Amphiphilic Random Copolymer, Xanthan Gum, and Solvents.

The surface morphology of a cosmetic film consisting of an amphiphilic random copolymer (methoxy polyethylene glycol-23 methacrylate/glyceryl diisostearate methacrylate copolymer, MPM-GDM) and solvents has been studied. The cosmetic film was prepared through the evaporation of water from a homogeneous aqueous mixture of MPM-GDM, xanthan gum, and solvents. MPM-GDM was soluble in water, monohydric alcohols, and 1,3-butylene glycol (1,3-BG), whereas it hardly dissolved in glycerin. The surface morphology was examined by changing the solvent composition of 1,3-BG (good solvent) and glycerin (poor solvent). Confocal laser scanning microscopy (CLSM) images of the cosmetic film showed that MPM-GDM spread through the whole film in the absence of glycerin, whereas the addition of glycerin led to the formation of a sea-island structure. It was assumed that the size of the MPM-GDM domain was determined by the balance between two factors: the miscibility (or the interfacial tension) of MPM-GDM against the solvents and the viscosity of the continuous phase. We also demonstrated that the concentration of both MPM-GDM and xanthan gum affected the surface morphology. Control of the surface morphology by changing the solubility of MPM-GDM is expected to be useful for improving the functionality and feel of cosmetic films.