Liquid-Liquid Phase Separation in Multicomponent Polymer Systems

This study focuses on experiments to understand the effect of additives on liquid-liquid phase separations (LLPS) in polymer solutions. In LLPS, distinct domains with different polymer concentrations form within a polymer solution at specific concentrations and temperatures. Polyethylene glycol(PEG) and dextran(DEX) have been used as an aqueous two phase system(ATPS) in this work. While the phase separation of PEG-DEX is understood, there has been less work on the effect of additional components on the kinetics and thermodynamics of the separation. We will present work on the effect of adding small amounts of biologically relevant compounds such as urea, tryptophan, formamide, tetramethyl urea and thiourea on the LLPS of PEG-DEX. Our initial studies show that the phase transition temperature is generally reduced, even with low concentrations of additives. Phase contrast imaging is done on samples to observe and analyze the phase separation, with Fourier analysis of the images yielding characteristics length scales vs. time and temperature. Moreover, differential dynamic microscopy (DDM) is used to characterize the effect of additives on the fluctuations near the transition temperature. Furthermore, temperature dependent UV-vis spectroscopy has been done to measure the turbidity, and kinetics of the phase separation.