Effects of the number of fatty acid residues on the phase behaviors of decaglycerol fatty acid esters

The effects of the number of fatty acid residues ( n) in decaglycerol fatty acid esters, i.e., decaglycerol laurates (abbreviated to (C 11) n G 10), on the phase behaviors of three laurate esters, (C 11) 1.9G 10, (C 11) 2.7G 10, and (C 11) 3.4G 10, were investigated. The unreacted decaglycerol remaining in each ester was removed by liquid extraction before use. (C 11) 1.9G 10 formed hexagonal liquid crystals in aqueous solutions, while (C 11) 2.7G 10 and (C 11) 3.4G 10, which are more hydrophobic than (C 11) 1.9G 10, formed lamellar liquid crystals. The cloud point in aqueous solution was measured for mixtures of these three esters. The cloud phenomenon was observed when the weight ratio of hydrophilic groups to the total surfactant ( W H/ W S) was around 0.6. The cloud point shifted to a markedly higher temperature, even with a slight increase in the W H/ W S ratio. The solubilization abilities of (C 11) n G 10 for the oils m-xylene and ( R)-(+)-limonene were also examined. When the W H/ W S ratio was between 0.60 and 0.64, (C 11) n G 10 formed microemulsions and lyotropic liquid crystals in the presence of water and the oils. These self-organized structures were stable, even above 90 °C. It is concluded that the phase behavior of (C 11) n G 10 are insensitive to temperature, but strongly dependent on both the W H/ W S ratio and the number of fatty acid residues ( n). The phase behaviors of decaglycerol laurates are studied and revealed that not sensitive to temperature, but strongly depend on the number of fatty acid residues ( n).