In water-polyoxyethylene(n) alkyl(m) ether (C
mEO
n; C
12EO
25, C
16EO
25, C
16EO
30, C
16EO
40, C
18EO
20, C
18;1EO
50, C
22EO
30) systems and water-polyoxyethylene(n) cholesterol ether (ChEO
30) system, the effect of chemical structures of surfactants and added perfume compounds on the stability of discontinuous cubic (I
1) phase were investigated. When the hydrophobic chain length of surfactant is kept constant, the maximum temperature up to which the I
1 phase can exist increases with increasing HLB value or the EO-chain length of surfactant. On the other hand, the maximum temperature of I
1 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 I
1 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/C
12EO
8/perfume systems. In general, the maximum temperature of ChEO
n systems is higher than that of C
mEO
n systems, because even amphiphilic polar perfume compounds do not largely penetrate in the surfactant palisade layer in ChEO
n systems. The interaction between cholesterol groups may be very strong, and therefore, may prevent the penetration of oil in the palisade layer.
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