Hydrogel microspheres, microgels, are soft colloidal particles swelling in water that consist of crosslinked hydrophilic (or amphiphilic) polymer chains. Different from bulk hydrogels, the physicochemical properties of colloidal-sized microgels can be quickly switched by changing external stimuli, e.g., temperature and pH changes. Due to their fascinating properties, microgels are expected to develop numerous applications. Microgels mainly have been synthesized by precipitation polymerization in water using N-isopropyl acrylamide (NIPAm) and crosslinker N,N′-methylenebis(acrylamide) (BIS), which allows to prepare large amounts of microgels with uniform size. The thermoresponsive pNIPAm microgels have a volume phase transition temperature, and the physicochemical properties might be affected by the degree of swelling, the softness, and the optical properties of the microgels which are governed by their structures. Thus, understanding correctly the structures of microgels is crucial to developing advanced microgel-based stimulus-responsive soft materials. Here, in this study, the nanostructures of microgels have been investigated using scattering method and temperature-controllable high-speed atomic force microscopy. Additionally, nanocomposite microgels including polystyrene nanoparticles will be discussed.

Design, fabrication, and characterization of microgels with defined nanostructures

ACS Fall 2021

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