Thermally induced phase separation and electrospinning methods for emerging membrane applications: A review

In this review, thermally induced phase separation (TIPS) and electrospinning methods for preparation of fluoropolymer membranes are assessed, particularly for the polyvinylidene fluoride (PVDF) and polyethylene chlorotrifluoroethylene membranes. This review focuses on controlling the membrane morphology from the thermodynamic and kinetic perspectives to understand the relationship between the membrane morphology and fabrication parameters. In addition, the current status of the nonsolvent induced phase separation (NIPS) method and the combined NIPS-TIPS (N-TIPS) method, which is a new emerging fabrication method, are discussed. The past literature data are compiled and an upperbound curve (permeability vs. tensile strength) is proposed for the TIPS-prepared PVDF membranes. Furthermore, the key parameters that control and determine the membrane morphology when using the electrospinning method are reviewed. Exploiting the unique advantages of the electrospinning method, our current understanding in controlling and fine-tuning the PVDF crystal polymorphism (i.e., ?-phase) is critically assessed.