"Chemical Determinants of the Phase Behavior and Viscoelasticity of Polyelectrolyte Complex Coacervates"
Complex coacervates are a class of polymeric materials formed by associative phase separation of charged polymers in aqueous solution. While the physical factors that determine the phase behavior and physical properties of these materials, such as temperature and salt concentration, are well-understood, far less is known about how chemical features of the polymers impact these properties. To address this problem, we use post-polymerization functionalization to prepare polymer libraries with varied charge density, hydrophobicity, and aromaticity, and characterize the phase behavior, complexation thermodynamics, and viscoelasticity of the resulting complexes. We show that hydrophobicity matters primarily when the hydrophobic units contain carbon chains of length 6 or more, and that cation-pi interactions substantially stabilize complexes of aromatic polyelectrolytes. This work brings new insights into the chemical interactions underlying the properties of polyelectrolyte complexes and coacervates and promises to inform development of materials with targeted properties under specific solution conditions.