(747c) Nonsolvent Induced Phase Separation in Films and 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. We find the existence of two kinetic regimes capable of generating microstructure via spinodal decomposition: one at times much shorter than the diffusion time of the nonsolvent and one at much longer times. We then use our model to explore and categorize the microstructures that emerge as geometry and composition is varied in each of these regimes.