Polymer adhesives are one of the most pervasive applications of polymers, and their critical role in today’s technologies has only grown. The reliance of numerous technologies, from electronics to medical care to building and construction, on polymer adhesion has vastly increased the range of environments and loading conditions that these interfaces encounter. This range of environments and conditions will grow as polymer interfaces are expected to play more important roles in protective gear and in robotic devices that are specifically designed to minimize human exposure to potentially harmful extremes. Additionally, the quantity of waste that is created due to polymer adhesion and adhesives is growing at significant rates. This waste is not only polymers directly used in bonding but also the bonded materials, which are typically difficult to separate in order to be recycled or upcycled efficiently. This research project will lead to new understanding of adhesion at polymer interfaces at extreme rates of loading and temperature change. This foundation will help to meet a deficiency in the fundamental knowledge of polymer interfacial properties at extreme conditions, and we anticipate that the results will guide the development of new protocols for separating interfaces that help build a more sustainable society. Graduate and undergraduate students who participate in this project will learn a broad range of skills, including polymer synthesis and formulation, characterization methods for adhesion, mechanical and thermal properties, and the development and implementation of custom instrumentation designed to address challenges at the forefront of technology. They will also develop writing, management, mentoring, and presentation skills. Additionally, the team of researchers will launch a new K-12 outreach program geared toward under-represented minority students throughout the Western Massachusetts region to help inspire future careers in STEM.
PART 2: TECHNICAL SUMMARY
While polymer interfacial strength has been studied classically, open questions, and seemingly contradictory results, remain unresolved in how material structure controls the deformation of interfaces loaded, mechanically and thermally, at high rates. The PI's group will combine a new experimental method, called power amplified dynamic mechanical analysis (PADMA), with model materials to provide insight and pathways for controlling polymer interfacial strength. Three model polymer systems based on poly(n-butyl acrylate), which is broadly used in many current commercial adhesives, will form the foundation of the study. Two systems will be designed with similar low strain and low strain rate properties but different large strain and large strain rate responses. This difference will be associated with the network’s crosslink junctions. These materials will provide insight into how the elasto-adhesion length scale evolves at high velocities and how this change is related to changes in the polymer network structure. The third materials system, poly(n-butyl acrylate)-co-poly(dimethylacrylamide) hydrogels with controlled volume fractions of water, will provide insight into how localized phase transitions initiated by high rate thermal changes alter interfacial separation. Specifically, the size and interconnectivity of water swollen domains will be related to changes in interfacial strength when loaded at high thermal rates. Overall, the results will contribute to the limited, yet growing, knowledge base of polymer properties at high rates, especially at interfaces. This knowledge will lead to new methods for separating polymer interfaces with decreased energy and without the need for harmful solvents.
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.
