PH-Dependent Aggregation Behavior and Emulsion Stability of Comb-Like Surfactant Containing PEO Grafts

Abstract

The aggregation behavior of the comb-like surfactant, poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether) (SMA-M), prepared via the one-pot method, at surface and in solution, was investigated by equilibrium surface tension, rheological technology, and transmission electron microscopy (TEM). The emulsion prepared from n-decane/water/C13E7 was used as a model system to determine the influence of SMA-M on the stability of the emulsion. The equilibrium surface tensions of SMA-M solution with various pH were measured. The adsorption data, that is, the saturation surface excess concentration (Γmax) and the minimum area (A min) were evaluated using the average monomeric molecular weight (M nA ). The results showed that Γmax decreased with the increase of pH, but the A min enlarged with the increase of pH. The results of the steady-state shear experiment indicated that the aggregate structure of the as-prepared comb-like surfactant SMA-M in aqueous solution evolved from interlinked micelle-like aggregates to isolated inflated micelle-like aggregates, then to rod-like aggregates with the increasing pH, which were confirmed by the TEM images. The investigation of the stabilization of n-decane/water/C13E7/SMA-M emulsion system indicated that SMA-M obviously slows down the phase separation, and the most effectively stabilized sample was obtained at pH 5.0. Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.