Poly(ionic liquid) brush coated electrospun membrane: a useful platform for the development of functionalized membrane systems

Abstract

In this work, poly(ionic liquid) brushes were successfully grafted to the electrospun SiO₂ nanofiber surface with atom transfer radical polymerization (ATRP) technology. By adjusting the density of initiator sites on the nanofiber surface, the core–shell structure was fabricated, which could clearly be “seen” with transmission electron microscopy (TEM). Combining the unique properties of an ionic liquid and electrospun nanofibrous mat, this hierarchically structured membrane provides a useful platform for developing functionalized membrane systems. With counteranion exchange of the attached poly(ionic liquid) brushes, the properties and functionality of the prepared membrane can be easily adjusted or integrated on need. As a demonstration, such a membrane served as an nion-directed molecular gating system. With counteranion exchange, the surface properties of the membrane were reversibly altered between hydrophilic to hydrophobic, which makes pores withdraw or expel solvent molecules (H₂O), thus controlling the transport of probe molecules through the membrane. As a further example, electroactive polyoxometalate (POM) units were incorporated into the membrane through simple counteranion exchange, and a functionalized membrane with electroactivity was also achieved. In this work, various characterization techniques including infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical measurements were used to characterize the related membrane systems.