Dynamics of the phase inversion process

摘要

AbstractAn analysis of the dynamics of phase inversion based on mathematical modeling andin situexperimental observations is presented. Calculations based on ternary diffusion models illustrate the effects of casting film composition, evaporation time, and film thickness on the precipitation time and resulting polymer film profiles, which correlate with observed final morphologies. An experimental method based on the use of dark ground optics, interface visualization, and reflected light illumination is used forin situmonitoring of the mass transfer and phase separation dynamics during the quench step. Observations on the systems water—dimethylsulfoxide cellulose acetate and water—dioxane—cellulose acetate show regions in the films corresponding to gel formation and growth, instabilities associated with finger formation, and homogeneous ternary diffusion. Data for the kinetics of the diffusion and gel front motions show that both propagate as the square root of time with rates dependent on the bath—film compositions. Examples of interface structures characteristic of deep quenching and nucleated droplet growth are also shown. Semiquantitative analyses in terms of the ternary models developed earlier and a phenomenological model for diffusion in the growing gel are used to explain the trends seen. © 1992 John WileyS