Fabrication of Porous Phenyl Silsesquiazane and Poly(ethylene oxide) Nanofibers by Electrospinning and Nonsolvent-induced Phase Separation

A porous nanofiber web with a hierarchical pore structure was formed by electrospinning and nonsolvent-induced phase separation (NIPS) processes. Phenyl silsesquiazane (PSSQZ) containing 20% high-molecular-weight poly(ethylene oxide) (PEO) was electrospun to form a nanofiber web, where a mixture of high volatility solvent and low volatility nonsolvent induced the pores within the nanofibers through NIPS mechanism. The content of the polymers and the type and ratio of solvent/nonsolvent significantly affected pore formation, and a nanofiber web with a hierarchical pore structure was formed using 90/10 of PSSQZ/PEO, 80/20 of chloroform/decane, and 5 wt% total polymer content. The nanofiber web was then converted to inorganic nanofibers by heat treatment at 700 °C. However, the internal pore structure collapsed due to the low level of cross-linking during the heat treatment, forming hollow inorganic nanofibers.