Diblock copolymer stabilization of multi-wall carbon nanotubes in organic solvents and their use in composites

A versatile method for the preparation of dispersed nanotubes using polystyrene-b-polyisoprene diblock copolymers in different selective organic solvents is presented. Stable dispersions have been obtained in polar (DMF) and apolar (heptane) media depending on the selectivity of the diblock copolymers. They have been characterized by means of optical microscopy, TEM imaging and dynamic light scattering, showing the first demonstration of multiwall carbon nanotubes (MWCNTs) solutions with in situ characterization of diblock copolymer stabilization. The most effectively stabilized dispersions have been used to make nanotube/polystyrene composites. We find that the coating of the nanotubes by the diblock polymer does not prevent electrical transport, so that the system can exhibit a relatively high surface conductivity above the percolation threshold. The low percolation threshold experimentally determined is presumably due to weak attractive interactions between the nanotubes as the composites are dried. (c) 2006 Elsevier Ltd. All rights reserved.