(197g) Correlation and Sequence Effects in Complex Coacervation

Polymeric complex coacervates are mixtures of oppositely-charged polyelectrolytes that undergo liquid-liquid phase separation into polymer-rich and polymer-deficient phases. These materials are useful for a broad range of applications, such as encapsulants, drug delivery vehicles, tissue engineering scaffolds, and underwater adhesives. More fundamentally, their stability at high salt leads to physical environments that are hypothesized to be similar to the materials at the origins of life. The similarity between complex coacervates and biological materials has led to their recent emergence as a powerful motif in self-assembly. Currently, there are a number of theories describing complex coacervates, ranging from simplified Flory-Huggins-based approaches to highly sophisticated field theoretic approaches. These theories can reproduce general phase behaviors, however are limited when considering monomer-level charge sequence. We have developed new theoretical methods capable of demonstrating that the proximity of charges along the contour of a polyelectrolyte strongly affects complex coacervates. The theory is based on the Polymer Reference Interaction Site Model (PRISM) that captures molecular correlations of polymer molecules in a fashion that is more powerful than existing theories. Sequence and excluded volume are found to play a crucial role in coacervation, and reveals a cancellation of errors responsible for the success of more simplified theories. Strong sequence effects, however, suggest the ability to strongly tune interactions within coacervate materials and alter phase behavior. We follow this up with Monte Carlo computer simulations that demonstrate similar trends, and we can provide an initial glimpse at the rich behaviors that may be realized with sequence-control of monomers in complex coacervates.