Compliant Clients: Catechols Exhibit Enhanced Solubility and Stability in Diverse Complex Coacervates

Polyelectrolyte coacervates, with their greater-than-water density, low interfacial energy, shear thinning viscosity, and ability to undergo structural arrest, mediate the formation of diverse load-bearing macromolecular materials in living organisms as well as in industrial material fabrication. Coacervates, however, have other useful attributes that are challenging to study given the metastability of coacervate colloidal droplets and a lack of suitable analytical methods. We adopt solution electrochemistry and nuclear magnetic resonance measurements to obtain remarkable insights about coacervates as solvent media for low-molecular-weight catechols. When catechols are added to dispersions of coacervated polyelectrolytes, there are two significant consequences: (1) catechols preferentially partition up to 260-fold into the coacervate phase, and (2) coacervates stabilize catechol redox potentials by up to +200 mV relative to the equilibrium solution. The results suggest that the relationship between phase-separated polyelectrolytes and their client molecules is distinct from that existing in aqueous solution and has the potential for insulating many redox-unstable chemicals.