Chemical Engineering (ChE) Department Head John Klier reports that a ChE team consisting of himself, Shelly Peyton, and Sarah Perry is collaborating with Todd Emerick in the UMass Polymer Science and Engineering Department and Anna Balazs at the University of Pittsburgh to investigate a new class of materials, known intriguingly as “cryptic materials,” which undergo strengthening in response to mechanical deformation. Klier explains that these cryptic materials can be applied to a wide range of valuable applications, including biomaterials, contact lenses, absorbent materials, wound-healing materials, coatings, adhesives, high-performance composites, and many other applications.
According to Klier, “This work is very novel and has very recently attracted over $1.2 million in new funding from the National Science Foundation (NSF), with a focus on soft materials such as hydrogels, and the U.S. Army Research Office (ARO), which is supporting research on high-performance materials with exceptional increase in mechanical strength.”
Klier adds that cryptic materials “get stronger as they are deformed or ultrasonicated (or maybe even in the presence of loud music – although we have not tested that yet).”
As Klier explains, “These materials have already exhibited over four orders of magnitude increases in stiffness and strength in response to shear or ultrasonic activation. These remarkable properties are brought on by reversible and irreversible crosslinking that takes place when ‘cryptic’ domains that protect reactive functional groups unfold in response to mechanical stimulus.”
Klier says that these two research programs for the NSF and ARO span synthetic work, polymer characterization, and mechanical evaluation, as well as “theoretical work to fully exploit this new discovery.”
As Klier and his colleagues explain about their NSF research on hydrogels, they are a class of water-swollen polymer networks, and they represent an increasingly important category of materials in research and commerce. However, unlike some other types of polymeric materials, there is currently no simple robust mechanism to strengthen hydrogels on-demand. Building on-demand strengthening into these hydrogel systems would significantly enhance their real-world applications, say the researchers.
The researchers explain that their NSF work is aimed at providing a simple and triggered way to strengthen hydrogels on demand: “This project will create a way to strengthen gels by applying force to them, with specific applications toward better, more robust materials.”
As the research team says about its work for the ARO to develop high-performance cryptic materials applicable to coatings, adhesives, elastomer, and composite applications, “Using our expertise in modeling, materials chemistry, and mechanical characterization, our team of investigators will produce a new class of polymers that undergo tunable stiffening in response to applied forces and thereby exhibit new or enhanced properties upon mechanical deformation.”
The researchers say that their ARO project is inspired by the remarkable ability of biological macromolecules to undergo beneficial structural changes in response to force. As they observe, “Using theory-led design, we will create a new class of force-responsive materials, with a specific focus on stiffening via strain-induced exposure of reactive sites.”
The research team notes that biologically inspired computational models will guide the experimental effort, while synthetic chemistry will produce force-sensitive materials that achieve the desired mechano-responsive behavior.
In summary, say the researchers, “We expect our collaborative approach will lead to transformative routes to utilizing mechanical deformation to improve materials performance.” (January 2020)