Cryptic Hydrogels

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Non-Technical AbstractHydrogels are a class of material that can become swollen with water, and they represent an increasingly important category of materials in research and commerce. They are employed as biomaterials, contact lenses, absorbent materials, wound healing materials, water retention aids, coatings, adhesives, and many other applications. However, unlike many other type of plastic materials typically used in industry, these hydrogels are typically very weak, and there is currently no robust mechanism to strengthen the materials on-demand. Building this attribute into these hydrogel systems would significantly enhance their real-world applications. In sum, this process costs one to ten billion dollars, and seven to twenty years per drug. This project will create a way to strengthen gels by applying force to them, with specific applications toward better, more robust adhesives. They will also use this funding to create new educational opportunities for students. Specifically, high school women will be brought into the lab during the summer months, where they can work with these and other sophisticated materials and diverse researchers. Technical AbstractHydrogel and organogel networks are swollen, insoluble polymer networks made from soluble monomer precursors, and they are an increasingly important class of materials in research and commercial applications. Their uses are far-reaching in both academia and industry, as biomaterials and wound healing materials; controlled delivery materials and networks; contact lenses; coatings; and adhesives. One critical limitation for gels has been that, in comparison to industrial thermoplastic polymers, they cannot be strengthened in response to mechanical deformation. Building on-demand stiffening into gel systems could greatly broaden their full potential and utility in applications as stable and mechanically robust adhesives, coatings, fabricated articles, and potentially biomaterials. In this project, a team of three laboratories will 1) Create and characterize poly(ethylene glycol) (PEG) gels with strain-induced stiffening properties, both irreversible and electrostatic (reversible) crosslinks, 2) Incorporate shielding groups into the networks to tune their force sensitivity, and 3) apply this technology to mechanically-activated adhesives. These studies will establish fundamental relationships between molecular and environmental parameters and strain-triggered elastic modulus changes with a new class of materials. This work will provide the scientific foundation for hydrogel property control via strain-triggered stiffening or softening mechanisms. This contribution is significant because the eventual applications of this fundamental knowledge could apply to materials design for new hydrophilic materials as well as regenerative medicine and disease. Outreach objectives in this proposal will continue current efforts developed by the PIs in previous NSF-funded broader impacts in expanding engineering research opportunities tailored for high school girls.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.