(161o) Processing Dependence and Aging of the Coacervate-Precipitate Transition in Mixed Polyelectrolytes
AIChE Annual Meeting
Thursday, November 19, 2020 - 8:00am to 9:00am
Here, we show that the formation and aging of precipitates from oppositely-charged polyelectrolytes is highly sensitive to the mechanics of mixing. Using a series of mixing protocols spanning several orders of magnitude of Reynolds number, we show that the compositions where precipitates are observed shifts significantly with mixing type. Furthermore, by examining their aging and stability, we show that precipitates are not permanently arrested, but rather can be transient states that coexist with and age to form coacervate droplets over a broad range of conditions. This aging is also dependent on the mixing protocol, suggesting that mass transport effects dominate the early formation of precipitates. Video microscopy experiments used to track the initial growth and morphology of precipitates suggest that a diffusion-limited aggregation process, similar to flocculation in unstable colloidal dispersions, underlies the sensitivity of precipitate formation and relaxation to various mixing parameters. Our studies highlight the transient nature of the coacervate-precipitate transition, and open new opportunities for using mixing and flow to control material processing in mixed polyelectrolytes.