Microstructure formation phenomena in phase inversion membranes

Most structural studies of polymeric phase inversion membranes have focused on macrovoid formation, while the rich microstructure (size scale < 5 mu m ) has received little independent attention. We present a classification an d qualitative description of possible microstructures on the basis of phase diagram, kinetic, and connectivity considerations. Special attention is gi ven to the microstructural features resulting from a two-stage phase separa tion. Subsequently, our considerations are extended to the microstructure o f the skin and that of the macrofinger boundaries. Finally, the features of actual phase inversion microstructures are described and interpreted.