Title: Controlling crystal growth using polyelectrolytes

Abstract: In one form or another, polyelectrolyte additives are employed to control the formation of ionic crystals in a variety of contexts. As one example, engineers employ them as antiscalants to prevent the buildup of minerals on the interior of pipes. In a drastically different setting — the microenvironment in animal tissues in which collagen is mineralized to form bone — biological macromolecules bearing multiple phosphate groups enable the deposition of calcium salts on the interior of nanoscale fibrous scaffolds. In these processes, associative interactions between the polyelectrolyte and nanoscale amorphous ion clusters serve as kinetic barriers to the nucleation of stable crystals. In some contexts, these interactions drive a phase separation process that results in the formation of a mineral-rich liquid-like precursor phase. Such precursors can be manipulated with scaffolds and capillary forces to ultimately synthesize crystalline materials in highly non-equilibrium morphologies. This talk will cover some insights and applications related to liquid precursor phases (mostly of calcium carbonate) being explored in the Schroeder lab in the Department of Textile Engineering, Chemistry and Science. Our lab is able to manipulate such precursors using other additives to controllably trigger nucleation on-demand, activity we are able to rationalize using thermodynamic arguments. We have also developed methods to scaffold crystal deposition using readily available substrates, enabling the synthesis of functional materials at scale.

Tom Schroeder is an Assistant Professor in the Department of Textile Engineering, Chemistry and Science in the Wilson College of Textiles. Prior to joining NC State in 2022, he completed a postdoc in materials science in Joanna Aizenberg’s lab at Harvard, a Ph.D. in chemical engineering from University of Michigan (in Michael Mayer’s biophysics lab, with which he moved from Ann Arbor to the Adolphe Merkle Institute in Switzerland for nearly 3 years), and a bachelor’s degree in chemistry from Northwestern. Tom is broadly interested in bioinspired materials; his other specific foci include gels and ionic circuitry.