Comparison of different approaches to describe the thermotropic volume phase transition of smart microgels

Abstract The description of gel swelling by Flory and Rehner using the original Flory–Huggins interaction parameter for polymer–solvent cannot be applied to most smart microgels. Here, we compare descriptions curves such microgels series expansions $$\chi$$ ? with results Hill-like equation . We study N -isopropyl-acrylamide particles at different concentrations cross-linker N,N -methylenebisacrylamide. hydrodynamic radius $$R_{\mathrm {H}}$$ R H microgel is determined photon correlation spectroscopy. fits expansion nicely follow experimental data. However, already first-order expansion, computed $$\Theta$$ ? temperatures are not physically reasonable. Moreover, physical meaning parameters clear. equation, which recently introduced, yields a good all measured provides meaningful parameters. For instance, Hill $$\nu$$ ? corresponds number water molecules per network chain cooperatively leaving volume phase transition. Graphical abstract Different approaches model Flory-Huggins explored compared respect quality fit curves.