Institut Charles Sadron Event

Polyelectrolyte complex coacervation is an associative phase separation that occurs when oppositely charged polyelectrolytes (PE) form a polymer-dense phase, the complex coacervate (CC), in equilibrium with a polymer-lean supernatant (SN). Owing to the reversible nature of macroion pairing, CC offers recyclable alternatives to conventional polymer-based materials. However, challenges in controlling their phase behavior limit large-scale applications. This thesis investigated the relationship between phase behavior and mechanical properties across different synthetic PE systems. For strong linear PEs, an underexplored high-PE-concentration region of the phase diagram was examined, allowing construction of a comprehensive phase diagram spanning two-phase to one-phase regions. Rheological analysis using time-PE superposition revealed correlations between phase behavior and viscoelasticity. While salt addition is generally known to dissociate macroion pairs and results in a one-phase system, this work also probed the less studied high-salt region for a copolymer-based system. For weakly charged linear PEs, increasing salt concentration was found to drive associative toward segregative phase separation, progressively dehydrating the polymer-rich phase and excluding hydrophilic PE into the polymer-lean phase. Finally, branched weak PE was employed to assess the mechanical properties of dehydrated CC. Overall, this study identifies key parameters for tuning CC properties, deepens the understanding of the complex coacervation mechanism, and expands the potential of sustainable CC-based materials.