Poly(N-isopropylacrylamide) (pNIPAM) nanogels have attracted interest due to their thermal responsive behaviour close to body temperature. Probing the thermal stability of pNIPAM nanogels in a wide range of multivalent cationic electrolyte solutions is of interest due to the complex electrolytic nature of biological interactions. Therefore, in this study we focused on the phase interactions of the pNIPAM nanogels in the presence of multivalent cationic electrolytes (NaCI, KCI, and CaCI2). We investigated the deswelling, flocculating and thermal reversibility behaviour of pNIPAM nanogels over an electrolyte concentration gradient range (0.1 mM to 100 mM) and a temperature variant between 25 °C and 50 °C. In order to predict the flocculation of these colloidal nanogels, we implemented a Debye screening model that addresses the shielding effect of multivalent cationic electrolytes on these nanogel systems. This study sheds light on how the multivalent interactions and ionic charge density affects the deswelling and flocculation properties of the pNIPAM nanogels in a predictive way. In this presentation, I will discuss the limits of the deswelling (with a trend of CaCl2 &gt; KCl &gt; NaCl at a constant electrolyte concentration) and flocculating (with a trend of CaCl2 &gt; KCl = NaCl at a lower electrolyte concentration) behaviour of the pNIPAM nanogels with the aim of predicting the deswelling ability as a function of the deswelling power and shielding effect of the electrolytes. In this work, we also studied the thermal reversibility of the swelling behaviour which is related to the surface charge screening effect of the different cations.

Effect of multivalent interactions on the electrostatic stability of poly(N-isopropylacrylamide) nanogels

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