Nanoparticle Coupling to Hydrogel Networks: New Insights from Electroacoustic Spectroscopy
2017
Adibnia, Vahid | Cho, Kyoung W. | Hill, Reghan J.
Nanoparticle–hydrogel interactions are important in many applications. In drug delivery, for example, these control the release rate and may prevent nanoparticle (NP) migration from a targeted site. In this paper, electroacoustic spectroscopy is used to study the NP–hydrogel interaction, focusing on the influence of polymer adsorption and hydrogel composition. Electroacoustic spectroscopy is a powerful noninvasive tool to complement microrheological characterization. We study the interaction of polyacrylamide (PA) with laponite and silica NPs as model systems with strong and weak attraction, respectively. Stronger adsorption of PA on laponite compared to silica imparts distinctly different rheological properties to PA solutions and decreases the laponite mobility significantly more than silica when embedded in PA hydrogels. However, the mobilities of both NPs exhibit qualitatively similar variations with acrylamide and chemical cross-linker concentrations, as indicated by viscoelastic and electrokinetic characterizations. The electrokinetic charge changes with polymer concentration more than with the chemical cross-linker concentration, whereas elastic coupling increases with the polymer concentration and decreases with the chemical cross-linker concentration. These reflect significant physicochemical changes to the hydrogel microstructure from the NP doping, so optimization of material properties for a specific application must explicitly consider the NP–polymer pairing.
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