Microgels, colloidal particles formed from a polymer network, respond to external stimuli and are a model system for soft matter. Those based on PNIPAM are thermoresponsive: they collapse when the temperature exceeds 32°C. The study published in ACS Nano marks a turning point by introducing a new class of colloids: star-like thermoresponsive microgels, obtained by replacing the crosslinking agent with a more reactive one. This leads to the formation of a structure with a dense core and a corona of long, flexible arms, a complex architecture, like star polymers. Star polymers are known for their unique physical properties and vast application potential but are complex to synthesize and therefore not widely used. The discovery is twofold: these microgels have a much sharper volume transition, ideal for many applications, and they provide an accessible system for studying the dynamic behavior and ultra-soft interactions of star polymers.

Article: E. Ballin, F. Brasili, T. Papetti, J. Vialetto, M. Sztucki, S. Sennato, M. Laurati, E. Zaccarelli, Star-Like Thermoresponsive Microgels as an Emerging Class of Soft Nanocolloids, ACS Nano 2025, https://doi.org/10.1021/acsnano.5c08174