The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201806733.Polymeric porous media (PPM) are widely used as advanced materials, such as sound dampening foams, lithium-ion batteries, stretchable sensors, and biofilters. The functionality, reliability, and durability of these materials have a strong dependence on the microstructural patterns of PPM. One underlying mechanism for the formation of porosity in PPM is phase separation, which engenders polymer-rich and polymer-poor (pore) phases. Herein, the phase separation in polymer solutions is discussed from two different aspects: diffusion and hydrodynamic effects. For phase separation governed by diffusion, two novel morphological transitions are reviewed: "cluster-topercolation" and "percolation-to-droplets," which are attributed to an effect that the polymer-rich and the solvent-rich phases reach the equilibrium states asynchronously. In the case dictated by hydrodynamics, a deterministic nature for the microstructural evolution during phase separation is scrutinized. The deterministic nature is caused by an interfacial-tensiongradient (solutal Marangoni force), which can lead to directional movement of droplets as well as hydrodynamic instabilities during phase separation. Polymeric Porous Media

The performance and the application of membranes, which are usually produced from polymer solutions, are strongly determined by their porous microstructures. One important mechanism for producing the porous microstructures of membranes is polymerization-induced phase separation (PIPS). Here, we scrutinize PIPS by employing a Cahn–Hilliard–Navier–Stokes method coupling with the Flory–Huggins model. We focus on the formation of membranes via diffusion as well as capillary flow. We report several morphological evolution characteristics of PIPS: (1) an asynchronous effect, where the polymer-rich phase and the polymer-lean phase reach their equilibrium concentrations at different times, (2) a center-to-center movement and collision-induced collision of polymer-rich particles, (3) transition of network structures into polymer particles and rebuilding of network structures from polymer particles, (4) polymer ring patterns. We expect that these findings would shed light on complex microstructures of membranes and provide guidance for the fabrication of desired membranes.