Adsorption and Phase Behavior of PEO and PVP On Cationic Nanoparticles in the Protein Limit

The adsorption of PEO and PVP onto cationic nanoparticles is studied by ITC, DLS, SANS, and by depletion. Weak segmental adsorption of PEO onto the nanoparticles leads to depletion phase separation when c>c*. Stronger segmental adsorption of PVP leads to bridge flocculation for sub-monolayer adsorption and depletion phase separation when c>c*. The effects of polymer molecular weight and solution ionic strength are investigated. In buffer solution, multilayer adsorption is observed for PVP. The qualitative features of the depletion phase separation follow predictions from the PRISM model, which are opposite to that for the classical AO model. The results are interpreted within the physicochemical characterization of the particles, polymers, polymer-particle interactions and particle-particle interactions in the presence of polymer.