Synthesis of dendrimer-carbon nanotube conjugates

We describe the coupling between Carbon Nanotubes (CNTs) and a second-generation cyanophenyl-based dendrimer. The goal of our work is the synthesis of highly functionalized CNTs without provoking damage to the conjugated π-system. One approach is the attachment of dendrimers with a high density of functional groups to the CNTs. These groups serve as anchor points for further reactions. With this aim, we have carried out a primary modification on CNTs by the use of 1,3 dipolar cycloaddition reaction. We have employed Single Wall Carbon Nanotubes (SWNTs) as well as Multi Wall Carbon Nanotubes (MWNTs) obtaining 238 μmol and 511 μmol of pyrrolidine groups per gram, respectively. The amount of amino groups introduced in the system was measured by the Kaiser test as well as thermogravimetric analyses. As a second step, dendrimer incorporation was performed by carbodiimide chemistry. Thermogravimetric Analysis, Raman Spectroscopy and Atomic Force Microscopy characterization techniques are reported for the characterization of the final CNT-dendrimer conjugate. The results show that the dendrimer has been attached covalently to the previously generated amine groups. Morphologically, the attached dendrimer with an estimated theoretical molecular length of 6.4 um, generates a wrapping of 8 nm thick around the CNTs walls.