“Bioinspired Thermodynamics of Polyelectrolyte Complex Coacervates”

Bio: Charles Sing is an Associate Professor of Chemical and Biomolecular Engineering at the University of Illinois at Urbana-Champaign. He received his BS and MS in polymer science from Case Western Reserve University in 2008, and his PhD in materials science from MIT in 2012. Prior to starting at Illinois in 2014, Charles was a postdoctoral fellow at Northwestern University. His research interests are broadly in the areas of computational and theoretical polymer physics; current projects focus on molecular and sequence properties of polyelectrolyte solutions, out-of-equilibrium rheology of semidilute polymers, polymers with nonlinear architectures, and charge and penetrant transport in polymers solutions and networks. He was recognized with an NSF CAREER Award in 2017, and in 2020 was recognized as an ACS PMSE Young Investigator and UIUC Helen Corley Petit scholar and was selected as one of AIChE’s ’35 Under 35’.

Abstract: Charged polymers known as polyelectrolytes have been studied for decades, however understanding their physical properties remains a persistent challenge for polymer scientists. This difficulty stems from the intricate interplay between length scales spanning as much as 3-4 orders of magnitude, which has stymied our understanding of a truly important class of polymers; polyelectrolytes are widely used in applications ranging from food additives to paints, and most biopolymers (proteins, DNA, polysaccharides) are also polyelectrolytes.

However, the complexity of charged polymers can be harnessed for molecular-level materials design. Inspired by sequence-specific behaviors in biomolecular condensates, intracellular structures that assemble in part by electrostatic interactions, we study phase separation phenomena in sequence-defined polyelectrolytes. We are specifically interested in a class of polyelectrolyte materials known as complex coacervates, which are aqueous solutions of oppositely-charged macromolecules and salt that can exhibit associative phase separation. We pursue an integrated computational and theoretical study, in collaboration with experimentalists, to demonstrate that coacervates are highly sensitive to the precise patterning of charges and other chemical and physical aspects of their environment. We elucidate the key molecular features that play a large role in coacervate thermodynamics. Building upon these insights, we demonstrate how coacervate phase behavior and assembly can be strongly tuned via specific charge sequences, pH, and macroion structure. Ultimately, our goal is to establish molecular-level design rules to facilitate the tailored creation of materials based on complex coacervation that can both illuminate self-assembly phenomena found in nature, and find utility across a wide range of real-world applications.

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