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.

Effects of dioctadecyl dimethyl ammonium chloride on the rheological behavior of behenyl trimethyl ammonium chloride/1-hexadecanol/water ternary system.

The effects of dioctadecyl dimethyl ammonium chloride (DODAC) on the rheological properties of ternary systems consisting of behenyl trimethyl ammonium chloride (C22TAC), 1-hexadecanol (C16OH), and water are studied to improve the long-term stability and to establish the preparation method of cosmetic products. The basic ternary systems behave as solids at low stresses, due to the formation of lamella liquid crystals called alpha gel. The additions of DODAC to ternary systems cause the rupture of alpha gel structures and transformation to vesicles. The structures of molecular assemblies are confirmed through particle size distribution, differential scanning calorimetry, and freeze fracture electron microscopy. The vesicle structures formed in coexistence of single-chain surfactant and double-chain surfactant are highly stable. Because the quaternary systems are considered to be constructed by the mixtures of alpha gel and vesicles at the appropriate concentrations of DODAC, the rheology can be controlled by the structural balance between them.