Seminar Speaker: Tom Schroeder, NC State

Polymers as Tunable Kinetic Barriers in Energy Transduction and Material Synthesis

Abstract

Many of the most important and complex processes that drive living systems rely on precise interactions between macromolecules (lipids, proteins, and nucleic acids) and small molecular or ionic species (water, salts, and metabolites). Macromolecules can serve as specific, responsive kinetic barriers that control transport processes, chemistry, and phase behavior. The successful deployment of this motif leads to emergent functional systems ranging from skeletons made out of collagen-templated salt crystals to networked neurons capable of staggering computational feats mediated by the opening and closing of ion channels. In this talk, I will describe past and current research projects in which my collaborators and I have used synthetic polymers instead of biological macromolecules to serve as kinetic barriers to control processes relevant to energy transduction and material fabrication. In one project, we assembled repeating sequences of discrete hydrogel units comprising high- and low-salinity reservoirs and charge-selective membranes in a manner inspired by the structure of the specialized organs of the electric eel. This yielded a modular electrical power source with voltage and current output that scaled with the quantity and geometry of the repeating gel units. In another project, we demonstrated the ability to control the fast, exothermic crystal growth of salt hydrate phase change materials by photopatterning a hydrogel matrix within a metastable solution before nucleation. Controlling the kinetics and spatial evolution of crystal growth enables control over the spatiotemporal evolution of heat waves, which can be coupled to downstream thermally activated processes. Currently, my group at NC State is examining crystal growth processes mediated by metastable “polymer-induced liquid precursors” of the type implicated in bone biomineralization. We have demonstrated the ability to trigger on-demand crystal nucleation from these metastable phases by exploiting the thermodynamics of polyelectrolyte solutions; we have plans to demonstrate the applicability of this technique to the fabrication of functional materials.

Biography

Tom Schroeder joined NC State’s Department of Textile Engineering, Chemistry and Science as an Assistant Professor in the fall of 2022. Prior to this, he was a postdoc in Materials Science and Mechanical Engineering in Joanna Aizenberg’s lab at Harvard. Tom received his Ph.D. in Chemical Engineering from the University of Michigan working in Michael Mayer’s lab; in the middle of his studies, he and the lab moved from Ann Arbor to the Adolphe Merkle Institute in Fribourg, Switzerland, where he spent nearly three happy years. He has been supported by the Swiss National Science Foundation’s Postdoc Mobility fellowship and the University of Michigan Cellular Biotechnology Training Program fellowship and was a 2021 Foresight Institute Fellow in the Molecular Machines subgroup. Tom is interested in how polymers can be used as controllable kinetic barriers in solution-phase processes, often as gels and most usefully in the context of energy transduction and crystal growth. Whenever he can, he seeks inspiration from the solutions that biology has evolved in response to nature’s problems. Outside of work, Tom has been enjoying spending time at NC State’s Crafts Center learning printmaking and ceramics.