Center for Functional Nanomaterials Seminar

I will highlight two examples of my research on mechanics and applications of self-assembled hierarchical architectures of nanomaterials. In the first example, I will present preparation of biomimetic polymer/clay nanocomposites with record-high strength and stiffness. (Podsiadlo et al., Science, 2007) Understanding of nanoscale mechanics, the interfacial molecular interactions, and achieving efficient interfacial load transfer between the inorganic nanomaterial and organic polymer matrix are key elements for successfully harnessing the exceptional nanoscale properties for macroscale structures. The ultimate development of my work is a 90% transparent in the visible range multilayered film with 50 vol.% loading of clay nanoparticles, tensile strength of 400 MPa, and modulus of elasticity of 110 GPa. The unique layered architecture of these materials has been explored for applications in gas barriers, flame retardant coatings, as well as biomedical coatings. In the second part, I will present my recent research on characterization of collective physical properties in self-assembled nanoparticle (NP) superlattices (SL). In these novel architectures NPs self-organize into periodic structures analogous to atomic crystals, with NPs serving the roles of artificial atoms. Precise positioning of the NPs in single, binary, and even ternary assemblies leads to novel collective optical, electronic, magnetic, and even mechanical properties. I will present the first experimental results from systematic evaluation of mechanical properties of 3D SLs using nanoindentation and in situ synchrotron X-ray diffraction techniques. The nanoindentation results showed truly “crystalline” behavior of the 3D SLs, with elastic modulus and hardness being at least 2x greater when compared to random films of the same NPs. These results show unique potential and opportunities for tuning interparticle interactions through application of mechanical force in these novel metamaterials.