Leveraging the Stability of Ionic Liquids in Processing Polyampholytes

Double network gels composed of polyampholytes have been shown to have both tough and strong properties due to both inter and intra electrostatic bonding. Upon deformation, the weaker bonds break and dissipate energy allowing the gel to be load bearing despite retaining up to 90% water. While these gels are suited for bulk applications such as the knee or achilles heel, it remains a challenge to fabricate thin films that can coat non-planer surfaces such as the hip joint. Traditional polyelectrolyte processing has used salt to screen bonds and move across the polyelectrolyte coacervate continuum. Upon evaporation of water, however, this salt can recrystallize and disrupt film morphology. In this work, an ionic liquid composed of choline chloride and urea is used to dissolve and rapidly deposit double network gels. Moreover, in contrast to salt processing, the ionic liquid is stable at ambient conditions. Finally, rheological studies and phase diagrams are presented to understand the interplay between ionic liquid, polyampholyte, and water.