Thermo-responsive polyacrylonitrile membranes prepared with poly(acrylonitrile-g-isopropylacrylamide) as an additive

Thermo-responsive polyacrylonitrile (PAN) membranes were prepared by the immersion precipitation phase inversion process using poly(acrylonitrile-graft-isopropylacrylamide) [P(AN-g-NIPAAm)] as an additive. This additive was synthesized by a facile approach based on the combination of reversible addition–fragmentation chain transfer and thiol-ene click chemistry followed by radical copolymerization. The graft copolymer was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Its side chains thermo-responsibility was determined by ultraviolet analysis and water contact angle measurement. Effects of P(AN-g-NIPAAm) addition on the morphologies of PAN membranes were investigated by scanning electron microscope. X-ray photoelectron spectroscopy was conducted at different take-off angles to elucidate the surface segregation of the amphiphilic graft copolymer in the prepared membranes. Results show that the hydrophilic PNIPAAm chains greatly segregate at the membrane surface, which endows these PAN membranes with obvious thermo-responsibility for water permeation.