Multi-responsive carbon nanotube gel prepared via ultrasound-induced assembly

Abstract

Hyperbranched poly(amido amine) is grown from the surface of carbon nanotubesvia a multi-step Michael addition reaction, hence the amido and amine units are linked onto the surface of carbon nanotubes. These amido and amine units can facilitate the assembly of carbon nanotubes with other functional polymersviahydrogen bonds. The external ultrasound-stimulus is found to induce the assembly of functionalized multi-walled carbon nanotubes with linear poly(amido amine) into a smart carbon nanotube gel viahydrogen bonds. The notable advantages of this method are that the gelation is very fast and controlled by ultrasound strength, the formed carbon nanotube gels are not only responsive to some mechanical stimuli such as vigorous agitating, but also responsive to some chemical stimuli such as water and acids. The carbon nanotubes are homogenously embedded in the gel network, and the sol–gel switching is easily realized via heating and ultrasonicating. It is interesting that sonication can untangle the bundles of MWNT via breaking the van der Waals forces between them to disperse MWNTs at high temperature, but induce the assembly of MWNTs functionalized with poly(amido amine) viahydrogen bonds into a smart carbon nanotube based gel at room temperature.