PHASE TRANSITIONS OF SEBUM 37 Table II List of Vehicles Evaluated for Their Effect on Model Sebum Chemical Source Propylene glycol (PG) Dimethyl isosorbide (DMI) Diethylene glycol monoethyl ether (Transcutol) Polyoxyethylene- 10-stearyl ether (POE- 10) Maleated soybean oil (Glycerid acid, MSO) Labrafil M 2125CS Labrafil M 1944CS Labrasol Phosphatidylcholine Glyceryl dilaurate (GDL) Isopropyl myristate (IPM) Oleic acid (OA) MP diol Sigma Chemical Co., St. Louis, MO Sigma Chemical Co., St. Louis, MO Sigma Chemical Co., St. Louis, MO Sigma Chemical Co., St. Louis, MO International Speciality Products, Wayne, NJ Gattafosse Corporation, Westwood, NJ Gattafosse Corporation, Westwood, NJ Gattafosse Corporation, Westwood, NJ Sigma Chemical Co., St. Louis, MO Sigma Chemical Co., St. Louis, MO Sigma Chemical Co., St. Louis, MO Sigma Chemical Co., St. Louis, MO L_vondell Chemical Worldwide= Inc l-ln•tnn T•'

38 JOURNAL OF COSMETIC SCIENCE 3.8 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 Mp-3 Mp-1 -5O -25 0 25 50 Temperature(øC) Figure 1. Typical thermogram of a model sebum. 75 100 -1 , -2 • Isopropyl Myristate • Transcutol •_• .•• Propylen•e Glycol • • Oleic acid Mp-1 Mp-2 • Dimethyl Isosorbide • Glycerin Mp-3 •/•Control (Model Sebum i i i i i i i -50 -30 -10 10 30 50 70 90 Temperature (øC) Figure 2. Thermogram showing the effect of different vehicles on the model sebum or control. the added fluidizer does not dissolve in the sebum, each of the two components will maintain their physical properties, including melting points. Of course, another situa- tion can occur, where a specific interaction between solute and solvent (e.g., complex-