Nonsolvent Induced Phase Separation in Polymer Droplets*

Nonsolvent induced phase separation (NIPS) occurs when a polymer solution is brought into contact with a miscible nonsolvent, leading to the precipitation of a polymer-rich phase. Because of its simplicity, NIPS processes are widely used to generate a variety of microstructures in polymer materials such as membranes and micro/nanoparticles. Despite its prevalence, predicting and controlling the microstructure generated by NIPS remains a difficult challenge, owing to the complex interactions between the diffusive transport, hydrodynamics and phase-separation kinetics in the process. In our approach, we use simulations of a phase-field model of a polymer solution to examine the effect of mass transfer, hydrodynamics and geometry on the formation of microstrucure. In particular, we study the NIPS process in polymer droplets, where we examine the effect of droplet size, shape, and composition on the resulting microstucture. We also examine the impact of finite solvent/nonsolvent miscibility on the kinetics and microstructure of the phase separation.