Microstructural Rearrangements in Triblock Polyelectrolyte Complex Hydrogels

We examine the swelling and dehydration-rehydration response of triblock polyelectrolyte complex (PEC) hydrogels using small-angle X-ray scattering and rheology to demonstrate that PEC hydrogel microstructures equilibrate readily into morphologies corresponding to <i>pristine</i> PEC hydrogels with comparable polymer contents. As such, we show that PEC hydrogels possess identical microstructures independent of the route employed to make them. We propose PEC domain fission as the dominant mechanism for these microstructural rearrangements. Furthermore, we show that mixing two fully formed PEC hydrogels with distinct microstructures leads to microstructural rearrangements, resulting in hydrogels with intermediate microstructure and viscoelastic properties of the individual PEC hydrogels. Our findings provide explicit experimental proof that PEC hydrogel microstructures are not kinetically trapped and have implications for their processing in diverse applications.