Electrostatic Interactions Control the Nanostructure of Conjugated Polyelectrolyte-Polymeric Ionic Liquid Blends

Polyelectrolyte complexation offers unique oppor-tunities to compatibilize polymers with very different backbone chemistries and to control the morphology of the resulting blend via electrostatic manipulation. In this study, we demonstrate the ability to formulate homogeneous complexes of a conjugated polyelectrolyte with a polymeric ionic liquid, utilizing the electrostatic attraction among their oppositely charged side chains. Variation of electrostatic parameters, such as counterion concen-tration or polymer charge fraction, tunes the morphology of these polymer complexes from homogeneously disordered blend to weakly structured microemulsion where the local ordering arises from backbone-immiscibility-induced microphase segregation. Our experimental observations are in qualitative agreement with both field-theoretic simulation and random-phase approximation calculations. Simulated morphology snapshots suggest and experimental evidence also indicates that the microphase-segregated complex likely takes on a cocontinuous microemulsion structure. Our findings show that ionic interactions are an effective pathway to compatibilize polymers at macroscopic length scales while achieving controlled nanostructures in these ionic blends. Such systems have great potential for engineering the nanostructure of polymers to tailor applications such as nanofiltration, catalysis, and energy storage, where local ordering can enhance the physical properties of an otherwise macroscopically homogeneous structure.

Automated summary

Polyelectrolyte complexation allows for the compatibilization of polymers with different chemistries and control over blend morphology via electrostatic manipulation. By varying electrostatic parameters, such as counterion concentration or polymer charge fraction, the morphology of polymer complexes can be tuned from a homogeneously disordered blend to a weakly structured microemulsion. These systems have great potential for engineering the nanostructure of polymers for applications such as nanofiltration, catalysis, and energy storage.