Hydrogels are water-laden polymer networks with applications in diverse areas including drug delivery, cell and tissue engineering, bioadhesives and tissue sealants and biosensing. This project will create novel types of self-assembled hydrogels composed of two interweaving polymeric networks, with one containing permanent linkages and the other comprising reversible linkages held together by attractive electrostatic interactions among oppositely charged polymers. These new materials will feature complex, hierarchical nanoscale structures and unique elastic, flow and adhesive properties, with relevance in development of the next generation of wet adhesives and tissue sealants. Furthermore, the planned experiments will advance our fundamental understanding of the assembly of charge-containing polymers and the mechanisms through which reversibly-linked networks support the slow, in-situ growth of permanently linked networks. In the broader context, this project will further the understanding and appreciation of polymeric and adhesive materials, polymer physics and chemistry, and advanced material characterization techniques to high school, undergraduate and graduate students through hands-on experiments and demonstrations, new courses and course modules, and regional research symposia, thus motivating the next generation of polymer scientists. In parallel, development of tutorials and interactive software data analysis tools for soft material characterization techniques will contribute to educate and expand the user base of these techniques and serve the broader scientific community.
Creating hydrogels with controlled cohesive and adhesive properties, during and after curing, remains a challenge. This project will institute design paradigms for creating polyelectrolyte complex-interpenetrating network (PEC-IPN) hydrogels featuring orthogonally tunable bulk and interfacial strengths and toughness. Fundamental studies of self-assembly of oppositely charged block polyelectrolytes into polyelectrolyte complex (PEC) networks will elucidate their hierarchical structure, chain dynamics and mechanical properties, and the evolution of these physical attributes upon inclusion of small molecule or polymeric additives in PEC hydrogels. Crosslinking of diverse chemically crosslinkable monomeric and polymeric precursors, incorporated in PEC hydrogels, will be demonstrated as routes to create PEC-IPN materials with controlled network microstructures. Furthermore, the proposed studies will reveal the enhancements in bulk elasticity and toughness of PEC-IPN hydrogels that emerge from stress dissipation in the self-assembled PEC domains constituting the PEC network. Consequently, PEC-IPN hydrogel adhesives with tuned bulk and interfacial mechanical properties will be developed, targeting potential applications as robust underwater adhesives and tissue sealants. Concurrently, this work will contribute towards establishing a knowledge base for PEC self-assemblies, analogous to the existing base for traditional amphiphilic block polymer assemblies. The proposed research will thus develop a family of versatile self-assembled PEC-based materials that rival yet are distinct from amphiphilic block polymer assemblies and expand the realm of their applications such as micellar drug and gene delivery vehicles. .
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
