Emulsions stabilized with hydrophobically modified poly(acrylic acid)

Abstract

Hydrophobically Modified (with alkylamide chain) linear Poly(acrylic acid) Sodium Salt (HMPAANa) of various degree of grafting (τ) and alkyl chain length (n) were synthesized and used as emulsifiers of n-dodecane/water (NaNO₃ 10⁻³M) system. Stability and flow properties of the resulting n-dodecane in water emulsions (dispersed phase volume fraction=0.5) were investigated as a function of τ (τ=0 to 10% in mol), n (n=12, 18) and polymer concentration (0–10%).

It was clearly shown that viscosification (via an associative mechanism of HMPAANa) of the external phase of emulsions is a key factor to explain dispersions breakdown. However, a complete description of the phenomenon could not be achieved without considering the adsorption of the polymer at the liquid-liquid interface which depends closely on τ and n. More generally, the behavior of emulsions was found to be described adequately by the degree of hydrophobicity of HMPAANa's using a simple model conjugating the effects of τ and n. As a matter of fact, the model was also found to provide a satisfactory description of HMPAANa's aqueous solutions as well, so that a good picture of emulsions properties can be deduced from the polymer behavior in water.