The synergistic effect of using polystyrene-grafted multi-walled carbon nanotubes (PSgMWCNT) and a surfactant in the dispersion of MWCNT in a self-assembled poly(styrene-b-isoprene-b-styrene) (SIS) block copolymer is reported. The functionalization of MWCNT with polystyrene achieved by the grafting-from approach is not enough to disperse them in the SIS block copolymer. However, a high dispersion of PSgMWCNT in SIS is achieved when dodecanethiol (DT) was added through composite preparation, without affecting the SIS capacity to self-assemble in ordered cylinders. Suspensions of PSgMWCNT without DT and not functionalized MWCNT with DT presented low stability forming aggregates in less than 10 min. On the contrary, the stability of PSgMWCNT suspension in the presence of DT was dramatically enhanced to more than two weeks. This synergistic effect is due to interactions between PSgMWCNT and DT molecules, as proved by UV-Vis spectroscopy. (C) 2011 Elsevier Ltd. All rights reserved.