Abstract
The majority of polymer membranes are fabricated through phase separation (PS) processes within polymer/solvent systems. Thermodynamic demixing results in the formation of two distinct phases: a rich polymer phase, which solidifies to form the final membrane structure, and a lean polymer phase, which generates the pores following solvent extraction. A critical challenge in this process is the precise control of the morphogenesis mechanisms, which significantly impact the final membrane architecture and, consequently, its functional properties, including permeability and selectivity. The kinetics of phase separation firstly depends on the region in the phase diagram. In the metastable region, the phase separation is governed by nucleation and growth mechanism. In the instable region (spinodal region), the dynamics of phase separation is spontaneous and is driven by spinodal decomposition. In this case, the Cahn-Hilliard equation is used to describe the phase separation dynamics. This equation describes the relaxation dynamics of order parameters driven by the local minimization of the Ginzburg-Landau free energy functional[1]. However, for other mechanisms, such as nucleation and growth, alternative theoretical descriptions may be required. In this study, we conducted simulations of phase separation in both Temperature Induced Phase Separation (TIPS) binary (polymer/solvent) and Non-solvent Induced Phase Separation (NIPS) in ternary (polymer/solvent/non-solvent) systems using 2D and 3D models. The thermodynamic potential was characterized by the Flory-Huggins-De Gennes theory [2]. By systematically varying the initial concentrations and the depth of thermal quenching in the polymer solution, we analyzed the influence of these factors on the phase separation dynamics. The simulation results were further examined using Fourier transform analysis to extract quantitative data on the growth laws governing the formation of microstructures. This work elucidates the impact of processing conditions and operational parameters on the morphology of polymer membranes, as well as on the kinetics of phase separation, providing insights that are crucial for optimizing membrane design and performance.