Using Polymer-Surfactant Charge Ratio to Control Synergistic Flocculation of Anionic Particulate Dispersions

This study investigates the flocculation induced destabilization of particulate dispersions by oppositely charged polymer-surfactant complexes, with a particular focus on controlling interactions by modulating the charge ratio Z, (where Z = [+(polymer)]/[-(surfactant)]) via [-(surfactant)] at fixed C-polymer. Cationic hydroxyethyl cellulose (cat-HEC) polymer-sodium dodecylsulfate (SDS) complexes were prepared with either excess polymer (Z > 1) or surfactant (Z < 1) charges. Anionic particulate dispersions (Ludox and polystyrene-butadiene Latex) were then exposed to the complexes, and solvent relaxation NMR was used to characterize the particle surfaces before and after exposure. In both particulate dispersions, flocculation induced destabilization was enhanced after exposure to cat-HEC-SDS complexes with Z > 1, leaving any excess particle surfaces uncoated after gentle centrifugation. However, complexes with Z < 1 showed no adsorption and destabilization in the Ludox dispersions and only slight destabilization in the Latex dispersions due to possible hydrophobic interactions. Substituting SDS for non-ionic surfactant (C12E6) showed no additional destabilization of the dispersions, but post-centrifugation relaxation rates indicated preferential adsorption of C12E6 onto the particle surfaces. Since the dominant forces are electrostatic, this study highlights the possibility of controlling the interactions between oppositely charged polymer-surfactant complexes and particle surfaces by modulating Z through [-(surfactant)].

Automated summary

This study investigates how the destabilization of particulate dispersions is influenced by oppositely charged polymer-surfactant complexes. The results show that complexes with a charge ratio greater than 1 enhance the destabilization, while complexes with a charge ratio less than 1 do not show adsorption and destabilization. This study highlights the possibility of controlling the interactions between polymer-surfactant complexes and particle surfaces by modulating the charge ratio.