Poroelastic flows in polymeric materials under stress

When poroelastic solids are subject to stresses, these stresses couple ot the flow of the solvent, and can drive solvent migration. Such phenomena arise in numerous settings, from cross-linked polymer networks such as gels, to soils and biological materials. While the theory for poroelasticity is well-developed, the material properties of the network and solvent can alter the material response when the network is loaded. Here, we use a combination of elastomers swollen with polymeric oils of the same chemistry as the network as well as hydrogels to explore the behavior of gel networks at their limits. Using high-resolution microscopy and 3d particle tracking, we characterize the full deformation field during the loading process. We find that pre-swollen elastomer networks fail at a lower relative stretch and stress than elastomer networks in the absense of solvent. We also find that for pre-cracked hydrogels immersed in a solvent bath, the crack imbibes a substantial amount of liquid as the crack advances, leading to a non-trivial rate dependence of the crack driving force as a function of the crack speed. Together these findings illuminate how solvent migration can significantly alter the failure of swollen polymer networks, while providing a validation of existing poroelastic fracture theory.