Inhibition of Water Crystallization by 3D Confinement in Supramolecular Hydrogels

1606685 PI: Vogt, Bryan Title: Inhibition of Water Crystallization by 3D Confinement in Supramolecular Hydrogels Water is critical for sustaining life, yet it still remains a puzzle with regard to full understanding of its properties. Its thermodynamics is highly anomalous with multiple solid-state phases including several amorphous states. When confined to small spaces, water exhibits different thermodynamic states, including a resistance to crystallization. Similarly, the function of proteins is driven by modulation of the hydration and structure of water locally, which can inhibit ice crystallization, but synthetic analogs have been challenging to achieve. The main idea of this proposal is that a hydrogel crosslinked by hydrophobic associations is a good model of water under confinement that mimics natural systems. The proposed research will employ a supramolecular hydrogel, crosslinked by hydrophobic associations, as a model to study the dynamics of water under confinement that better mimics natural systems than porous inorganics. The working hypothesis is that the nanoscale hydrophobic domains, at sufficient concentration, can confine water to yield supercooled water with fast dynamics. The research addresses fundamental questions in the physics of supercooled water, which may solve problems in the low temperature use of hydrogels (e.g., fracture when water expands upon freezing), an important commercial technology. Supramolecular hydrogels with dynamic crosslinks formed by self-assembly of hydrophobic nanodomains in copolymers of dimethyl acrylamide, a water soluble monomer, and 2-N-ethylperfluorooctane sulfonamidoethyl acrylate, a hydrophobic monomer, exhibit a well-defined nanostructure with smaller than 15 nm hydrophilic regions separating the hydrophobic nanodomains. The copolymer composition can be varied to tailor the length scale of water confinement. This proposed project focuses on understanding and controlling the dynamics of supercooled water in hydrogels. The proposed research seeks to 1) understand how the structure of hydrogels correlates with suppressed ice formation, 2) determine the effect of the hydrophilic polymer on supercooling efficacy, and 3) develop structure-property relationships to describe and predict the distribution of water states within supramolecular hydrogels as a function of chemistry and composition. A wide array of sophisticated characterization tools will be employed to study freezing thermodynamics and dynamics of water. In addition to training graduate students, the PIs plan to engage undergraduate and high school students in interdisciplinary research projects and recruit minority students into STEM careers. Proposed outreach activities will include hands-on demonstrations and discussions of hydrogels and water properties with local K-12 students and distribution of videos of ice formation and hydrogels in collaboration with the Akron Global Polymer Academy.