Effect of Added Perfume on the Stability of Discontinuous Cubic Phase

In water-polyoxyethylene(n) alkyl(m) ether (CmEOn; C12EO25, C16EO25, C16EO30, C16EO40, C18EO20, C18;1EO50, C22EO30) systems and water-polyoxyethylene(n) cholesterol ether (ChEO30) system, the effect of chemical structures of surfactants and added perfume compounds on the stability of discontinuous cubic (I1) phase were investigated. When the hydrophobic chain length of surfactant is kept constant, the maximum temperature up to which the I1 phase can exist increases with increasing HLB value or the EO-chain length of surfactant. On the other hand, the maximum temperature of I1 phase increases with increasing the molecular size of surfactant at constant HLB value. Upon addition of hydrocarbon-type perfume, d -limonene (LN), the maximum temperature of I1 phase is almost unchanged, whereas it decreases largely upon addition of amphiphilic polar oil, such as α-hexyl cinnamic aldehyde (HCA), β-ionone (IN), benzyl acetate (BA), linalool (LL), geraniol (GL), eugenol (EL), and cis -3-hexenol (HL), and is in order LN>HCA>IN>BA>LL>GL>EL>HL, which is the same as the HLB temperature in the water/C12EO8/perfume systems. In general, the maximum temperature of ChEOn systems is higher than that of CmEOn systems, because even amphiphilic polar perfume compounds do not largely penetrate in the surfactant palisade layer in ChEOn systems. The interaction between cholesterol groups may be very strong, and therefore, may prevent the penetration of oil in the palisade layer.