Polyelectrolyte Complex-Interpenetrating Polymer Networks Hydrogels*

Polyelectrolyte complex (PEC) hydrogels are three-dimensional polymer networks comprising oppositely charged ABA triblock polyelectrolytes with the electrostatically assembled domains composed of highly dense oppositely charged blocks serving as netpoints. PEC hydrogels self-assemble rapidly, are stimuli-responsiveness, and possess self-healing attributes, enabling potential applications in drug delivery, 3-D bioprinting, and wet adhesion technologies. However, the application-specific requirements demand a precise tunability of hierarchical structures and mechanical properties. To enhance the tunability of structure and properties of PEC hydrogels, we have developed a strategy to fabricate polyelectrolyte complex-interpenetrating polymer network (PEC-IPN) hydrogels, comprising a PEC network and a covalent network. We will demonstrate the generality of the approach by discussing hydrogels consisting of four different photocurable precursors - 4-arm poly (ethylene glycol) acrylate, poly (ethylene glycol) diacrylate, gelatin methacryloyl, and acrylamide - individually interpenetrated with the PEC networks to form a series of PEC-IPN hydrogels. All these hydrogels not only maintain diverse microstructures but also exhibit superior mechanical properties regardless of their distinct polymer shapes, polymer origin, molecular weights, crosslinking density, and crosslinking mechanisms, indicating a universal approach to engineer PEC-IPN hydrogels. We envision the versatility of our approach to broaden the application of PEC-based self-assembled materials in diverse biomedical research fields.