Gelation in carbon nanotube/polymer composites

The physical gelation in carbon nanotubes (CNTs)/polycarbonate composites was revealed by rheological analysis (Winter–Chambon method), based on the data reported by Paul [Polymer 43 (2002) 3247]. The gelation concentration cg, the relaxation exponent n and the gel strength Sg characterizing the critical gel point for the composites are 1.6 wt%, 0.75 and 770 Pa sn, respectively, which are comparable with those found for polymer gels. In fact, the gel points coincide with the percolation threshold of the electrical conductivity and the high strength in CNT/polymer composite applications. The new kind of physical gel originates from a combination of entanglement of CNTs and interactions between CNTs and polymer chains, instead of the chemical bonding or physical interactions in previous polymer gels.