2024 AIChE Annual Meeting
Utilizing Low Volume Samples to Construct Phase Diagrams for Coacervate Systems
Complex coacervation, a liquid-liquid phase separation phenomenon driven by electrostatic interactions of two oppositely charged polyelectrolytes, is a topic of growing interest in the biomedicine and biological communities. A large part of this investigation focuses on where this complexation occurs, commonly illustrated through binodal curves outlining the two-phase region. With industrial polyelectrolytes, large sample volumes (mililiters or larger) of both the dense liquid phase, the coacervate, and the surrounding dilute phase, the supernatant, can be generated and analyzed. When using biologically relevant polyelectrolytes, such as proteins, enzymes, peptides, etc., small sample volumes (microliters) are obtained. Single large volume samples may be made to generate a handful of points to create a binodal curve, though without the same degree of detail as binodal curves utilizing industrial polymers. Here, we are developing a method to utilize small sample volumes focusing on the supernatant phase with absorbance, emission, and conductivity readings as well as material balances of both phases to create a more detailed map of the binodal curve. Absorbance readings are performed after the polymers are fluorescently tagged. We initially focused on using poly(styrene sulfonate sodium salt) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) to form complex coacervates as a point of comparison between what has been done already in the literature and our method. This process will then be applied to more biologically relevant systems where large sample volumes are difficult to make, specifically poly(L-lysine) and poly(D,L-glutamate). By building these binodal curves, we will have a more accurate representation of where phase separation occurs and can more readily compare how different solution conditions (i.e., salt, pH) change the phase envelope.