Core/Shell Hydrogel Nanoparticles
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This contribution introduces the synthesis of poly(N-isopropylacrylamide) (pNIPAm)-based core/shell microgels and gives an overview of investigations involving the physical properties of such systems. Core/shell microgels are created via two-stage “seed-and-feed” precipitation polymerization. Core particles serve as preexisting nuclei onto which a hydrogel-forming polymer of a different composition (the shell) is added. The physical properties of the resultant particles are then analyzed with photon correlation spectroscopy (PCS) and fluorescence resonance energy transfer (FRET). Investigations herein show how the overall particle behavior differs between core and core/shell systems. Addition of a shell impacts the swelling behavior of the core component and varies with shell thickness. Particle behavior can be explained by considering the preparation method, where a radial crosslinker density gradient is created, resulting in a distribution of polymer network densities in the core and shell components.