ABSTRACT
The unique porous morphology of nanofiber membranes (NMs) makes them suitable for a broad range of practical applications. However, the fabrication of mesoporous NMs from commodity polymers remains challenging. This chapter describes a simple NM fabrication technique based on phase separation in polymer solutions that avoids the use of special polymer templates and elaborate processing. In particular, thermally induced gelation driven by polymer crystallization provides physical gels as NM precursors, and a reticular framework of thin nanofibers is subsequently obtained by solvent exchange and drying. NMs made of engineering plastics are shown to comprise thermally stable mesopores and hold great promise for thermal insulation–related applications. A method based on flash-freezing nanocrystallization (inspired by ice-templated and freeze-casting methods) affords macrovoid-free NMs with uniform pore diameters of 10–100 nm, allowing interconnected mesoporous structures with high specific surface areas of >300 m2/g to be obtained in the form of thin films, flat sheets, fibers, and monoliths. The fabricated NMs can function as advanced separation materials for separation and purification applications, e.g., as high-performance gas filters, liquid-permeable separation membranes, and adsorbents for carbon dioxide, organic vapors, and oil contaminants.
