Multiresponsive Supramolecular Poly(N-isopropylacrylamide) Microgels

Stimuli-responsive microgels are of great interest not only in fundamental research but also in a broad range of applications. In this study, we synthesize multiresponsive supramolecular poly(N-isopropylacrylamide) (PNIPAM) microgels using a homemade metallo-supramolecular cross-linker (SC) instead of the commonly used N,N′-methylenebis(acrylamide) (BIS). Originally, the supramolecular cross-linker is based on a coordination complex, which endows the microgels with salt responsiveness and degradability, in addition to their thermoresponsive properties as expected from PNIPAM-based materials. Afterward, the use of sodium dodecyl sulfate (SDS) in the conventional dispersion polymerization synthesis not only allows a microgel size tuning but also originally permits the successful incorporation of hydrophilic positively charged cross-linkers. By combining scanning electron microscopy (SEM) observations and light scattering measurements, we can evidence the core–shell-like structure of these new supramolecular microgels and its evolution with the cross-linker content. Finally, such well-controlled multiresponsive microgels could be relevant to stabilize smart emulsions or to perform drug delivery.