Viscosity reduction of HPAM solutions induced by silica nanoparticle additives

We discuss a plausible interpretation in which electrostatic interactions govern how nanoparticles influence the conformation of polyelectrolyte chains, in contrast to the more commonly assumed mechanisms dominated by hydrogen bonding or adsorption. Based on these considerations, we propose a phenomenological model in which changes in the relative distribution of nanoparticles with respect to polymer chains serve as a microscopic origin of the viscosity variation. The model captures the observed non-monotonic rheological trends and provides a semi-quantitative description of the crossover as the polymer concentration varies. These findings highlight the role of electrostatic interactions in the rheology of HPAM-silica nanoparticle mixtures and offer guidance for tuning viscosity within this specific polyelectrolyte-nanoparticle system.