The goal of the proposed research is to study particle dynamics and relaxation in so-called soft glassy materials. Such materials are printable functional inks for additive manufacturing, fluids for batteries and fuel cells, and pharmaceutical formulations. Successful completion of this study could lead to the manufacturing of new types of fluids with properties tailored to specific engineering applications.
It is proposed to develop a general framework for understanding how particle dynamics in jammed suspensions (nanoparticles in polymers) impact the transition from diffusive to hyperdiffusive dynamics. Recent reports on terminal relaxations in soft glasses have found that they are invariably and surprisingly hyperdiffusive. Hyperdiffusive relaxations are in fact now thought to be a characteristic of the soft glassy state and to reflect a material's out-of-equilibrium response to internal stresses, which are either built in at the glass transition or build up due to a variety of reasons. The PI and his group have recently discovered a class of soft glasses comprised of hairy nanoparticles that manifest a series of contradictory traits: (i) they are jammed and glassy; (ii) they manifest an accessible Newtonian flow regime and are able to reach equilibrium; (iii) they show little signs of aging; and (iv) they exhibit hyperdiffusive relaxations on long length and time scales. However, it is argued that the contradictory behavior is only superficial, and the dynamics of the system can reveal the fundamental behavior leading to these traits. They plan to use hairy nanoparticles as model systems, and a battery of experiments (photon correlation spectroscopies, small-angle X-ray scattering, mechanical rheometry, dielectric relaxation) and theory to shed light on the fundamental origins of hyperdiffusive relaxations in soft glasses. What makes this work exciting is that it goes after general models for dynamics of soft glasses, i.e., it looks to relate findings from experiments performed on limited time scales to dynamics in soft glasses on extended timescales. In addition to graduate education, plans to reach out to K-12 students and their teachers are laid out.