Abstract:

Factors affecting water solubilization in four-component nonionic microemulsion systems stabilized by polyol nonionic surfactants (sucrose esters) have been investigated. The effect of changing the chain length of alcohol (used as cosurfactant) and the lipophilic moiety of surfactant have been explored. The maximum water solubilization in the isotropic region (at oil/n-butanol ratio of 1) was 47, 23 and 55 wt.% for sucrose stearate (S-1570), sucrose laurate (L-1695) and sucrose palmitate (P-1570), respectively. Replacing the triglyceride oil (MCT) by dodecane caused a decrease in the water solubilization (40 wt.%) for sucrose stearate with an oil/n-butanol ratio of 1. The empirical BSO (Bansal, Shah, O'Connell) \[\1] equation which was derived as an empirical condition for maximum water solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alcohol) and oil chain lengths, i.e. N-S = N-O + N-A, where N-S, N-O, N-A are the surfactant chain lengths, oil and alcohol, respectively, was re-examined for this type of surfactants. This study demonstrates that a maximum water solubilization is obtained when the N-S = (N-O +/- 3) + N-A for N-S is greater than 14; when N-S is less than 14, this equation cannot predict the maximum water solubilization. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.