CBE Seminar (Zoom): Structural Evolution and Dynamics of Polyelectrolyte Complexes in Solid-to-liquid Phase Transitions

Abstract: Polyelectrolyte complexes (PECs, or associative phase separation of oppositely charged polymers in water) are a versatile class of soft materials that are present in both technological and biological worlds. Depending on the choice of polyelectrolytes, PECs can form solids to liquids, driven by the alignment of discrete ionic pairs that can be reversibly broken or formed with salt. Developing a more robust, fundamental understanding of the static and dynamic properties of ionic macromolecules along this solid-to-liquid continuum remains a grand challenge in polymer science and engineering. This talk describes a puzzle we encountered while investigating a controllably synthesized styrenic PEC system: as salt is sprinkled into a solution to break up associating ionic pairs between the oppositely charged polymers, why do solid-like PEC materials stiffen before transitioning into a sticky viscoelastic fluid? In this talk, we will piece together how rheology, phase behavior, and small-angle X-ray scattering collectively revealed the molecular-level interactions at play, giving rise to these highly unusual and potentially useful properties.

Bio: Jeff Ting (he/him) received his bachelor's degree in chemical engineering at the University of Texas. He received his doctorate in chemical engineering from the University of Minnesota (2016), where he worked with Frank Bates and Theresa Reineke on synthesizing tunable polymers for oral drug delivery. Afterward, Ting worked as a postdoctoral fellow in Matt Tirrell’s group at the University of Chicago Pritzker School of Molecular Engineering, as part of the Center for Hierarchical Materials Design (CHiMaD) supported by NIST and the Materials Genome Initiative. He recently started as a senior polymer scientist at 3M in Minneapolis, Minnesota; his current projects are part of the materials informatics platform in the Corporate Research Materials Laboratory. Outside of work, Ting enjoys running (marathon training in non-pandemic times), STEM outreach/engagement, and baking. Ting can be found on Twitter (@J_Ting1) or LinkedIn (jting1).