Multiresponsive polyanionic microgels with inverse pH responsive behavior by encapsulation of polycationic nanogels

Intelligent, stimuli‐responsive hydrogels have great utility in various fields spanning biomedical technology, separations, and catalysis. Their overall response to surrounding fluids may be further tailored to a specific application by incorporation of one or more intelligent responses within one material, known as multiresponsive hydrogels. This is a report on the facile synthesis and characterization of poly(methacrylic acid‐co‐N‐vinylpyrrolidone) microgels encapsulating polycationic nanogels (70–100 nm) to incorporate inverse pH responsive behavior within a single hydrogel. Potentiometric titration and pH swelling studies reveal a swelling response dependent on both pH and crosslinking agent. Additionally, a protein and a small molecule are loaded and released to evaluate the pH‐dependent binding affinity. Such a material could exhibit unique protein‐binding capacity and pH‐responsive behavior for use in separation or drug delivery applications.