A review on models and simulations of membrane formation via phase inversion processes

Abstract

Phase inversion processes, in which a polymer is transformed from a thin solution film into a solid matrix upon exposure to another gas/liquid phase or a temperature change, represent the most widely used manufacturing technique for polymeric membranes. However, the level of understanding of the connection between process variables and final membrane structure remains surprisingly empirical. Modeling efforts have largely been based on heuristics that correlate experimentally observed pore structures with process conditions, using thermodynamic phase diagrams and macroscopic transport models. Recent developments have added mesoscopic phase field approaches and molecular simulations to the array of modeling techniques applied to this problem. These latest developments hold the promise of delivering accurate, directly visualized representations of membrane pore structures formed by a given process. This article firstly provides an overview of the capabilities and limitations of the different modeling techniques and then focuses on how they have been developed and applied over the last 40 years to aid our understanding of membrane formation via phase inversion processes, especially nonsolvent induced phase separation (wet-casting), vapor/evaporation induced phase separation (dry-casting), and thermally-driven. Meanwhile, current challenges and future prospects, such as linking techniques across length and time scales as well as capturing the detailed effects of polymer crystallization, are also discussed. This review aims to offer inspiration for further progress in the field of modeling development for membrane preparation by phase inversion processes.