Noncovalent Grafting of Carbon Nanotubes with Triblock Terpolymers: Toward Patchy 1D Hybrids

The chemical structure and high aspect ratio of carbon nanotubes (CNTs) give rise to numerous exceptional physical properties but are also the origin for their intrinsic tendency to agglomerate. Since the full potential of CNTs is harnessed in homogeneous dispersions, e.g. in a polymer matrix, bundling of CNTs must be suppressed by compatibilizing unfavorable interfaces. We present a robust, noncovalent functionalization of multiwalled CNTs via physical grafting of polystyrene-<i>block</i>-polyethylene-<i>block</i>-poly­(methyl methacrylate) (SEM) triblock terpolymers to the CNT surface in organic media. In an ultrasound-assisted approach at ambient temperature, the polyethylene (PE) middle block of SEM strongly adsorbs to the CNTs surface, yielding long-term stable dispersions of well-separated 1D hybrids with up to 3 wt % CNT content. Importantly, the strong affinity of PE toward CNTs prevents polymer desorption irrespective of the solvent conditions. The incompatible polystyrene (PS) and poly­(methyl methacrylate) (PMMA) end blocks of SEM self-assemble into alternating PS/PMMA corona patches and provide excellent steric stabilization for the CNTs. Shorter PS and PMMA blocks give access to dispersions with higher CNT concentration and are more efficient in stabilizing longer CNTs. Unlike covalent functionalization methods, our approach preserves the conjugated sp²-structure of the CNTs and provides an efficient, simple and time-saving method for the preparation of polymer stabilized CNTs. The patchy PS/PMMA corona of the 1D hybrids is able to adapt to the surrounding environment as demonstrated on efficient high-content blending of PMMA with 5 wt % of well-dispersed CNT/SEM hybrids