Ward Thompson: October 2021 Sutton Family Research Impact Award Recipient

The Department congratulates Dr. Ward Thompson on receiving the October 2021 Sutton Family Research Impact Award! Please read more about his research below. 

Identical Water Dynamics in Acrylamide Hydrogels, Polymers, and Monomers in Solution: Ultrafast IR Spectroscopy and Molecular Dynamics Simulations

Sean A. Roget, Zeke A. Piskulich, Ward H. Thompson,* and Michael D. Fayer* Journal of the American Chemical Society, 2021, 143, 14855-14868

Hydrogels are cross-linked polymer networks that can absorb large amounts of water, making them useful in applications ranging from disposable diapers to contact lenses.  However, the effects of the hydrogel on the structure and dynamics of the absorbed water are still not fully understood. This is a significant limitation because the water makes up the majority of the volume of the swelled hydrogel.  A recent experimental-theoretical study of the water dynamics in polyacrylamide solutions and hydrogels revealed surprising insights.  Zeke Piskulich, a graduate student in the Thompson group, carried out modeling studies in coordination with nonlinear infrared spectroscopic measurements by Sean Roget and Prof. Michael Fayer at Stanford University.  The results show that, for a given mass concentration, the reorientational and vibrational dynamics of water are effectively independent of the polyacrylamide chain length, i.e., for acrylamide monomers, polymers, and hydrogels.  The modeling shows that this occurs because water molecules are only affected by the acrylamide if they are directly next to it (in the first solvation shell) and the fraction of such water molecules is nearly independent of chain length.  Importantly, this work demonstrates that the effect of the polyacrylamide hydrogel on the adsorbed water is not a confinement effect induced by the polymer network.