Materials World Network: Anomalous Thermoelasticity in Liquid Crystalline and Semicrystalline Polymer Networks

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This Inter-American collaboration between the US and UNAM-Cuernavaca in Mexico addresses outstanding questions concerning reversible (two-way) shape memory behavior in ordered polymers, recently discovered by the investigators to exist for both liquid crystalline and semicrystalline networks. Reversible shape memory is the process whereby, under a small applied stress, specimens undergo heating-induced contraction and cooling-induced elongation a sequence that can be repeated indefinitely for conversion of heat to work. While the phenomenon is exciting, of great potential use in soft actuation devices, and possibly universal among ordered polymer networks, fundamental studies are required to elucidate underlying mechanisms of the behavior. Thus, the collaborating investigators have conceived combining materials synthesis and solid-rheological characterization (US) with detailed, in-situ, microstructural characterization (Mexico) that will lead to quantitative and mechanistic understanding that connects molecular architecture, molecular interactions, nanostructure, and thermo-mechanical response. Using modern experimental approaches, the investigator establish design principles that guide the development of new shape memory polymers and processing schemes alike. By adopting a comparative analysis approach among multiple materials systems, the researchers anticipate discernment of both universal thermoelastic mechanisms and system-specific behavior. The investigators further endeavor to exploit the two-way shape memory behavior in the form of inventive devices, including design, fabrication, and testing.The collaboration functions through significant exchange of undergraduate, graduate, and postdoctoral researchers between the US (Mather's lab) and Mexico (Romo-Uribe's lab), engendering broad technical and cultural education alike. Network materials will be synthesized in the US, while in-situ x-ray deformation studies on the materials will be conducted in Mexico. As an outreach activity, the investigators establish CyberSTRETCH, a system for remote instrument control that enhances the collaboration and offers the broad impact potential for remote access to elastomer tensile testing for middle school and high school science, physics, or chemistry classes, revealing concepts of materials, strength, and mechanical design.This award is co-funded with the NSF Office of International Science and Engineering.