Three Distinct Scenarios under Polymer, Surfactant, and Colloidal Interaction

Abstract

Force measurement between emulsion droplets in the presence of a neutral polymer, poly(vinyl alcohol), and an ionic surfactant, sodium dodecyl sulfate, reveals that the interaction between polymer, surfactant, and colloid can lead to three distinct scenarios, depending on the sequence of adsorption of polymer and surfactant onto the colloidal interface. In the first two cases, where the colloidal interface is adsorbed with or without surfactant molecules, polymer−surfactant complexation occurs in the bulk phase but without being adsorbed at the interface. Under the above condition, the repulsive force between colloidal droplets is not significantly altered by polymer−surfactant complexes. In the third case, where the polymer is preadsorbed at the colloidal interface, polymer−surfactant interaction leads to dramatic changes in repulsive forces due to conformational changes of polymers at the interface, enhancing the stability of the colloid considerably.