A light scattering study of the influence of poly(ethylene glycol) on the droplet size and the interdroplet interaction in a water-in-oil-microemulsion

Abstract

Dynamic and static light scattering techniques were used to study the droplet size and the interdroplet interaction of w/o microemulsions consisting of cetyltrimethyl-ammonium bromide (CTAB), hexyl carbitol, toluene, water and poly(ethylene glycol). The results were analyzed in terms of a hard-sphere model with a perturbation. For the microemulsions without polymer, their droplet sizes increased only slightly (R=10.1 to 11.0 nm) and the perturbation became more attractive as the molar ratio of H2O/CTAB was raised from 50 to 82. In contrast, an increase in polymer concentration or polymer molecular weight not only increased the droplet sizes but also changed the perturbation to become more repulsive. In addition, it is envisaged that the interactions between the cationic groups of CTAB and the ether linkages of the poly(ethylene glycol) may also enhance the rigidity of the interfaces, hence the stability of the microemulsions. © 1989 Steinkopff.