Temperature Dependence of Electrophoretic Mobility and Hydrodynamic Radius of Microgels of Poly(-isopropylacrylamide).

Electrostatic interactions in charged microgels, which are dominated by the microgel net charge, play a crucial role in colloidal stabilization and loading of small, charged molecules. In this study, the temperature dependences of electrophoretic mobility and hydrodynamic radius were measured for a slightly ionized poly(-isopropylacrylamide) (PNIPA) microgel in a dilute suspension. A decrease in was observed in the temperature range between 30 °C and 35 °C, corresponding to the lower critical solution temperature of PNIPA, and an increase in || was observed in a higher temperature range between 34 °C and 37 °C. The analysis based on electrophoresis theory for spherical polyelectrolytes indicated that the net charge of the microgel decreased as the microgel was deswollen.