Hydrogels are commonly used as biological surrogates to study tissue response under high strain rate conditions. In this work, transient rheological properties of poly(ethylene glycol) diacrylate (PEGDA) hydrogels under Couette flow conditions are determined via molecular dynamics (MD) simulations and validated by high strain rate shear experiments. Using a self-similar solution to the power-law fluid model, a comparison of shear thickening behavior and transient state viscosity are made across length and time scales between MD simulations and experiments. Both ideal and nonideal hydrogel networks are considered to systematically study the role of water concentration, first-order loop defects and their corresponding topological influences. Higher shear-thickening exponents are observed for ideal hydrogels with lower PEGDA concentration due to differences in swelling. Nonideal hydrogels with lower effective crosslink functionalities, but with constant crosslink density, show lower shear thickening behavior due to nonaffine spatial rearrangement of crosslink junctions during deformation. Nonideal hydrogels with different crosslink densities, but with constant effective crosslink functionality, do not show appreciable differences in shear thickening behavior over the range of crosslink densities considered. The mechanisms of shear-thickening response are investigated by computing the average mesh size and the evolution of crosslink junction positions.
2021-04-07 08:00:00
