One form polyelectrolyte complexation of current interest is complex coacervation. This phenomenon is characterized by phase separation that occurs when oppositely charged polymers are dissolved in aqueous solution. Specifically, the polymers phase separate to form a polymer-rich phase known as a complex coacervate and a polymer-poor phase typically with a very low polymer concentration. By modifying the polymer architecture such that the polymers are composed of two blocks—one charged and one neutral—the polymers can assemble into micelles at low concentration and highly ordered microstructures exhibiting gel-like behavior at high concentrations. Due to the nature of these coacervates, they are responsive to a variety of stimuli. For example, the addition of salt screens the electrostatics and can result in the dissolution of a gel. Thus, they have potential as drug delivery systems and as tissue scaffolds. Areas of research to explore include polymer architecture (multi-arm star polymers and block copolymers), polymer concentration, and a variety of stimuli including temperature, salt concentration, and pH. In all cases, there would be a focus on going beyond equilibrium to probe dynamical quantities. Additionally, theoretical and computational work would be done in collaboration with experimental efforts both internal and external to NIST.