Polyampholyte Gelatin Adsorption to Colloidal Latex: pH and Electrolyte Effects on Acrylic and Polystyrene Latices

Polyampholytic gelatin adsorption onto two model, aqueous colloidal dispersions of like size and surface charge density, but varying hydrophobicity are reported. Adsorption isotherms and hydrodynamic layer thickness of the adsorbed gelatin layer are reported for variations of solution pH (above the gelatin IEP) and electrolyte concentration. A van't Hoff analysis of the temperature dependence of the dilute-limiting adsorption equilibrium constants provides evidence for adsorption driven by electrostatic polarization to like-charged surfaces, as well as additional hydrophobic interactions with polystyrene colloidal surfaces. It is demonstrated how these measurements can be used to predict the perikinetic stability of gelatin-coated colloidal latices and, hence, are useful for the rational formulation of dispersions containing polyampholytes.