Soft Microgels and Nanogels from a Physicochemical Perspective

Soft microgels and nanogels—solvent-swollen, crosslinked polymer particles spanning tens of nanometers to hundreds of micrometers—serve as model systems that bridge macromolecular and colloidal scales, advancing fundamental soft matter physical chemistry and enabling diverse applications. Their open, deformable architectures and soft interaction potentials underpin rapid, stimuli-responsive volume phase transitions to temperature, pH, ionic strength, solvent composition, pressure, and specific molecular cues, while facilitating mass exchange and adaptive behavior at interfaces. Progress in synthesis delivers monodisperse, functional microgels with tunable composition, size, crosslinking, shapes and morphologies. Advanced characterization reveals their heterogeneous internal architectures and interfacial structures. A quantitative, multi-parameter concept of “softness” links volume/shape changes, crosslinking, architecture, and particle interactions, with ultra-low crosslinked microgels exemplifying extreme deformability that impacts phase behavior and flow.