SGER: Interfacial Tension-induced Deformations in Soft Solids

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TECHNICAL SUMMARY:Two-way shape-memory polymers are materials that can reversibly switch between two different shapes in response to a trigger, such as change in temperature. We have proposed a new shape-memory concept based on interfacial tension-driven deformations in crosslinked polymer blends with an anisotropic two-phase morphology. This project will develop the scientific underpinnings of this new shape-memory concept. The first goal is to experimentally evaluate whether interfacial tension-driven deformations in solids are sufficiently large (strain ~ 10%) to be useful in two-way shape-memory applications. This portion of the project will be done on a model experimental system composed of polystyrene ellipsoids suspended in a crosslinked silicone rubber matrix; the shape change induced by melting the ellipsoids will be measured as a function of aspect ratio of the ellipsoids and the modulus of the silicone rubber. The second goal is to conduct numerical FEM calculations to calculate the magnitude of the shape change as a function of the interfacial tension, the size-scale of the two phase morphology, and the modulus of the solid.The result of this project will be an unambiguous determination of whether the new shape-memory concept has potential for two-way shape memory applications. NON-TECHNICAL SUMMARY:Two-way shape-memory polymers are advanced materials with numerous potential applications ranging from shape-morphing aircraft to mechanical actuation of parts of small machinery. Existing two-way shape-memory concepts require specialized polymers. We propose a broadly-generalizable strategy to design two-way shape-memory polymers, a strategy that will allow two-way shape memory to be realized using a wide range of polymer pairs. This project is intended to evaluate practical feasibility of this idea. If this exploratory project shows that interfacial tension-driven deformations in solids are sufficiently large, we will undertake future research to implement the new shape-memory concept using practical polymers. One post-doctoral fellow and one undergraduate will be trained during the project. The research will foster collaborations with the PI's colleagues in Mechanical Engineering and in Mathematics.