Grafting an Amphiphilic Block Copolymer to Magnetic-Functionalized Carbon Nanotubes and Their Nanochannels in Membranes

In this paper, a poly­(methyl methacrylate)-block-poly­(ethylene glycol methacrylate) [PMMA-b-P­(PEGMA)] copolymer is synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Magnetic-functionalized carbon nanotubes (mCNTs-SH) are grafted with different linear polymers on the surface by UV-initiated click chemical reaction. A poly­(vinylidene fluoride) (PVDF) composite membrane containing oriented magnetic CNTs (mCNTs) was achieved. Fourier transform infrared (FTIR), gas chromatography, proton nuclear magnetic resonance (¹H NMR), and gel permeation chromatography (GPC) were used to verify the P­(PEGMA)-b-PMMA-alkynyl structures. Vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to analyze the magnetic response state of magnetically functionalized CNTs, the influence of copolymers with different block contents on the graft rate, and the surface morphology of magnetically functionalized CNTs, respectively. The molecular weight of P­(PEGMA)-b-PMMA, which grafts to the mCNT surface, reaches 17 099 g·mol^–1, together with a maximum graft rate of 40.2%. The surface-grafted mCNTs also show superparamagnetic performance with the saturation magnetic response strength of 13.0 emu/g. When mCNTs are oriented in the composite membrane, the pure water flux increases by more than 60% compared to the pure PVDF membrane. The double interface layer mCNT/PVDF composite membrane has a lower water contact angle (62.8°) and a higher pure water flux (6.5 LMH) than the single interface layer mCNT/PVDF composite membrane with nanochannels.