Hierarchical, Porous Hydrogels Demonstrating Structurally Dependent Mechanical Properties

The unique properties of natural tissues are derived from highly complex arrangements of biomolecules spanning several orders of magnitude. Although replicating tissue properties is of great interest, little consideration has been given to mimicking their natural structures. Here, we demonstrate a process by which porous microstructures are incorporated into hydrogels via rapid spinodal decomposition of amphiphilic ABA triblock copolymer solutions when injected into water. At the nanoscale, the hydrophobic chain-ends of the block copolymer self-assemble into a network of micelle cores bridged by the hydrophilic mid-blocks. Simultaneously, the diffusion of the solvent triggers rapid spinodal decomposition, leaving micron-sized voids within the micelle network. In this work, we show how the pores introduce an additional deformation mode in the hydrogels, which strongly influences the mechanical properties of the hydrogels. The gels exhibit both high elasticity and extreme softness yet can reversibly deform to multiple times their initial length with no hysteresis. We investigate factors influencing the porous microstructure and mechanical properties, such as relative block composition and initial solution conditions. This research presents an exciting class of new materials, with diverse applications and an opportunity to further explore the complex physics of block-copolymer self-assembly.