Vortex-fluidic-mediated phase separation of polyethylene glycol and aqueous potassium phosphate characterised by real-time neutron imaging and scattering

Abstract

The phase separation of polyethylene glycol (PEG) and aqueous potassium phosphate is slow under conventional batch processing. Herein, we investigate the instantaneous phase separation of this system through thin film shearing in a vortex fluid device (VFD), monitored in real time using in situ small-angle neutron scattering (SANS) and neutron imaging. The SANS data for the aqueous two-phase system (ATPS) are best fitted with the Debye model, indicating that PEG molecules adopt a Gaussian coil structure under shear in the presence of potassium phosphate. Notably, when mixed in the VFD, the radius of gyration (Rg) of PEG molecules differed from that observed under diffusion-controlled conditions in a stationary cuvette. Shearing in the presence of potassium phosphate further altered the Gaussian coil structure of PEG, as indicated by a decrease in Rg. Real-time monitoring of PEG structural changes in both monophasic and biphasic systems has thus been established. This approach is important for understanding fluid regimes and their applications in biphasic purification and beyond.