Gels of carbon nanotubes and a nonionic surfactant prepared by mechanical grinding

Mixtures of carbon nanotubes (CNTs), including multi-wall CNTs and single-wall CNTs, and polyoxyethylene(12) tridecyl ether (POETE), a nonionic surfactant and a fluid at room temperature, became gels after mechanical grinding. The heavily entangled multi-wall or single-wall CNTs debundled during the grinding and dispersed with fewer bundles in POETE. The mechanism for the gel formation was studied by the dynamic mechanical measurements and scanning electron microscopy. The results suggest that the formation of the CNT/POETE gel is the result of the physical-crosslinking CNT networks, mediated by the van der Waals interaction between CNTs and the nonionic surfactant. The gels were stable from room temperature up to 200 degrees C and did not shrivel even in vacuum. The CNT/POETE gels were electrically conductive and could be processed into conductive CNT films by coating the CNT/POETE gels on a substrate by a doctor blade and subsequent heating. POETE was removed during the heating, while the heating did not degrade the CNTs. The CNT films had a conductivity of about 13 S cm(-1) and had good adhesion to the substrate. (C) 2009 Elsevier Ltd. All rights reserved.