Charged polymers known as <i>polyelectrolytes</i> 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 used as components of food additives and paints, and many biopolymers (proteins, DNA, polysaccharides) are charged.<br/> <br/>Despite challenges in understanding polyelectrolytes, they are a versatile class of polymers amenable to molecular-level materials design. To demonstrate, we examine how polymer monomer sequence can be used to engineer self-assembly in a class of polyelectrolyte materials known as complex coacervates. Complex coacervates are aqueous solutions composed of oppositely-charged polyelectrolytes and salt that undergo an associative phase separation process. We use simulation and theory, along with close experimental collaboration, to demonstrate that coacervates are highly sensitive to the precise placement of molecular charge. We elucidate the key molecular features that govern coacervate thermodynamics, and demonstrate how coacervate phase behavior can be strongly tuned via specific charge sequences using a combination of theory and simulation. Arbitrary charge sequences can be understood using our theoretical formalisms, revealing how polyelectrolyte charge fraction, contour charge monomer proximity, and charge blockiness contribute to the strength of electrostatic interactions. We show how principles of sequence-defined polyelectrolytes provide the foundation to study coacervate-driven assembly on length scales ranging from monomer-level structure to block copolymer nanophase separation and block polyampholytes.

Tuning polyelectrolyte assembly via charged monomer sequence

ACS Fall 2020 Virtual Meeting

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