Graphoepitaxial assembly of carbon nanotubes on polysynthetic twins assisted by synergistic secondary interactions

Based on the solid-solid transition during cooling, the polysynthetic twins of hexamethylbenzene were found to evolve with featured saw-tooth surface ledges of both micrometer and nanometer scales. These parallel arrays of surface ledges were recognized capable of guiding the annealing-induced assembly of carbon nanotubes in the medium of amorphous polyhexylthiophene. According to deciphered crystallographic background of saw-tooth ledges, the heights of evolved ledges were estimated to be around 4-6 nm merely, lower than the diameters of stacked nanotubes. Hence, instead of restricted assembly behavior, the preferential association of carbon nanotubes along shallow valleys between ledges is realized as the governing mechanism. Without viscous polymer medium, normally the graphoepitaxy behaviors occur on artificial surface patterns. For the graphoepitaxy of carbon nanotubes on arrays of nature saw-tooth ledges, synergistic interactions between nanotubes and surrounding polyhexylthiophenes medium contribute to moderate the crystallization of surrounding polyhexylthiophenes and also the thermal motion of nanotubes. Following the graphoepitaxial stacking of carbon nanotubes, succeeding crystallization of polyhexylthiophene medium on stacked nanotube bundles results in oriented arrays of hybrid shish-kebab superstructures and stabilize prior guided stacking of carbon nanotubes. According to unveiled results and structural analyses, this study deciphers an original mechanism capable of regulating the assembly behaviors of carbon nanotubes in polymeric medium on twin crystals, which manifests a feasible route to result in oriented arrays of shish-kebab superstructures. (C) 2017 Elsevier Ltd. All rights reserved.