Arrested Mobility Effects on the Spinodal Decomposition of Ternary Polymer Solutions

Many polymer membranes are made by immersion precipitation: a polymer solution film is immersed in a nonsolvent bath, inducing phase separation of the film into a polymer-rich phase that becomes the membrane matrix and a polymer-poor phase that becomes the membrane pores. Microstructure formation of these membranes is still not fully understood, given the interdepedendence of the processes involved: the mass transfer through the film-bath interface, the phase separation of the film, the coarsening of domains, and finally the glass transition that arrests the microstructure. In this work, we use phase-field models of the ternary system to solve the coupled convection-diffusion and momentum equations that describe membrane formation. We model the glass transition using mobility and viscosity contrasts between the polymer-rich and polymer-poor phases. We report how the glassy dynamics changes the microstructures formed by bulk spinodal decomposition. We also study how mass transfer between the bath and film changes with the formation of a glassy interface.