LAMELLAR LIQUID CRYSTAL 31 from 0 to 54% by weight. The solubilization of vitamin E acetate in the lameliar liquid is shown in Figure 2 for compositions along the lines through the liquid crystalline region in Figure 1. The solubilization for low water content was small (Figure 3), increasing strongly for maximum solvent at medium water content and reduced for the highest water/triethanolamine ratios. Figure 4 illustrates the trend with a maximum solubilization of 63% by weight at a TEA/water weight ratio of approximately one. The results are related to the dimensions in the lameliar liquid crystal as revealed by the low-angle x-ray reflections, giving the interlayer spacings of the lamellar structure (Figure 5). At first the variation in the triethanolamine/oleic acid ratio gave a constant interlayer spacing (Figure 6), while the water-containing structures (Figure 7) gave an increase of spacing with water content, more accentuated for lower triethanolamine/oleic acid ratios. The importance of water is illustrated by the variation of interlayer spacing with the triethanolamine/water ratio for constant oleic acid weight percent (Figure 8). High water content gave a pronounced increase in interlayer spacings. The influence of vitamin E acetate on the interlayer spacings are shown in Figures 9-12. The added vitamin E acetate had no influence on the interlayer spacing in the non- aqueous system (Figure 9). With water present (Figure 10), addition of vitamin E acetate gave a small change of interlayer spacing of the order of a few angstrom for an addition of 6% or less (by weight) vitamin E acetate. The interlayer spacing at no water content remained constant, but the slope was increased for increased vitamin E acetate content. Higher vitamin E contents required a slight change of the TEA/OLA weight ratio from 35/65 to 38/62. TEA/Water 100/0 80/20 60/40 OLA VE VE VE VE 40/60 25/75 20/80 18/82 OLA Figure 2. The region of the lamellar liquid crystal in vitamin E acetate (VE), oleic acid (OLA), and triethanolamine (TEA)/water solutions. Weight ratios of triethanolamine to water are given.

32 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS WATER / / / / / / / TEA OLA Figure 3. Three-dimensional representation of the solubilization of vitamin E acetate. 60 40 •- 30 o 20 10 Figure 4 TEN (TEA+Water) (wt/wt) Figure 4. Maximum solubilization into the lameliar liquid (Figure 3) crystal as a function of the trieth- anolamine/warer weight fraction. The presence of vitamin E acetate significantly changed the interlayer spacing depen- dence on the water content (Figure 11). Vitamin E acetate content in the range 8-30 percent gave an increase both in the extrapolated value to zero water content and the slope. The influence by vitamin E acetate becomes much stronger when water and triethanolamine are considered the solvent (Figure 12).