The Dynamics of Polymeric Microgels with Varying Crosslinker Concentration

Polymeric microgels synthesized by crosslinking amphiphilic polymer chains exhibit a reversible volume phase transition under the effect of environmental conditions such as temperature of a solution. The common behavior of these microgels is to deswell from a large to small size with an increase in temperature above the transition. Microgels in this study were synthesized by crosslinking a polysaccharide in a surfactant solution. When varying the amount of crosslinker by a factor of a hundred, three apparent behavioral regimes emerged from light scattering measurements: at low crosslinker concentrations, microgels deswelled and became more diffusive with temperature increase, at mid-range crosslinker concentrations they didn’t significantly change their size with temperature, and, at high concentrations, microgels showed a reversed behavior, where they grew and became less diffusive with increase in temperature. These apparent regimes are possibly due to nonuniform crosslinker distribution in the polymer microgel, which becomes more prevalent at large concentrations of the crosslinker.