An amphiphilic Gemini-shape hexa-peri-hexabenzocoronene (1) with azide functionalities self-assembles to form graphitic nanotubes whose interior and exterior surfaces can be post-functionalized by "click chemistry". A click reaction of the nanotubes with bulky macromolecules such as a dendronized alkyne (G2-alkyne) takes place site-selectively on the exterior surface of the nanotubes, leaving the azide functionalities on the interior surface mostly intact. A subsequent click reaction of the resulting nanotubes with alkynes having a much smaller steric bulk allows the remaining azide groups to be funtionalized, affording radially diblock graphitic nanotubes.