(265g) Tough, Rapidly Swelling Thermoplastic Elastomer Hydrogels for Hemorrhage Control

Bain, E., US Army Research Laboratory
Beyer, F. L., US Army Research Laboratory
Mrozek, R. A., US Army Research Laboratory
Lenhart, J. L., US Army Research Laboratory
Uncontrolled hemorrhage accounted for 80-90% of potentially survivable deaths of US soldiers over the past 15 years, a majority of which involved truncal or junctional wounds that could not be treated by tourniquet. Materials that rapidly absorb large amounts of water when inserted into a wound have shown promise to control hemorrhage by concentrating clotting factors and sealing the wound cavity. However, materials generally become weaker in proportion to swelling, causing first and second generation granular hemostatic agents to break apart in the wound, leaving debris that must be surgically removed from the body. We present here a tough, rapidly swelling polymer hydrogel based on commodity thermoplastic elastomers with potential application as a component in portable, durable, simple to apply, rapidly effective, and low cost hemostatic dressings. The swollen material has comparable toughness to current “tough” hydrogels, supporting intact removal from wounds, but can absorb up to 800 wt% water in just seconds, potentially facilitating rapid hemorrhage stabilization. Fast swelling and toughness are achieved via a continuous ionic soft phase supported by nanophase-separated hydrophobic glassy domains, as probed by transmission electron microscopy and neutron scattering. A material with optimized composition takes up 250 wt% water in < 1 minute under physiological conditions, and can be stretched up to double its length at 1 MPa stress without breaking while swollen. The composition based on simple free-radical polymerization is easily tunable, making this a low cost and versatile material platform.