oil phases used are simple saturated or unsaturated hydrocar-The effect of a polymer oil, polydimethyl siloxane, on the phase bons; however, the possibility of using polymer oils as one behavior of the water/C 12 EO 6 /isopropyl myristate (IPM) system of the components in formulating microemulsions has rarely has been studied. Since the polymer oil is completely soluble in been studied and the phase behavior of such systems are IPM, it was dissolved in IPM and the solutions were used as the less known (5, 6). Silicone oils are polymer liquids widely oil phase to study its effect. The presence of polymer increases the used in cosmetics, lubricants, toiletries, etc. ( 7). Therefore, hydrophobic nature of IPM and thereby decreases the solubilizaphase behavioral studies incorporating these oils are industrition of oil into the surfactant phase (microemulsion). Moreover, ally important. Katayama et al. studied microemulsions with at a certain range of silicone oil concentration in the IPM, a foursilicone oils. They found that the presence of hydrophilic phase body consisting of excess water, excess oil, and two surfactant phases is formed within the ternary system. The two surfac-groups (NH 2 ) in the silicone oil is a criterion for the formatant phases are designated as D (with bicontinuous type of struction of single-phase microemulsions (5).
ture) and D (with L 3 type of structure). Careful phase behavioral
Hydrophilic groups normally penetrate the surfactant palistudies revealed that, with increasing silicone oil concentration, a sade layer and thus stabilize the microemulsions. Interestthree-phase region containing water phase, D phase, and an oilingly, polydimethyl siloxane, as an oil phase, has difficulty rich D phase develops within the system and this region overlaps forming single-phase microemulsions. In addition, phase bewith the normal three-phase region of the system containing the havioral studies using this oil are also difficult as the clean water, D, and oil phases to give a four-phase body. The order of phase separation is seldom obtained. These difficulties can various phases from top to bottom in the four-phase body is oil, be minimized by dissolving this oil in a suitable solvent and D, D, and water. α§ 1997 Academic Press then using it as an oil phase. In a similar study, Kabalnov