Molecular-resolved imaging of the Hierarchical Self-Assembly of a conductive polymer at single-walled carbon nanotube interfaces

Molecular-resolved real-space images of self-assembled structures of the conductive polymer regioregular poly(3-hexylthiophene) (rrP3HT) on single-walled carbon nanotube (SWNT) substrates were obtained using scanning tunneling microscopy (STM). The STM images revealed that the adsorbed polymer formed a 10 nm thick coating on some SWNT´s in agreement with previous transmission electron microscopy results. This thickness corresponds to a coating of ~25 layers of polymer on SWNT, assuming that pi-pi interactions between rrP3HT layers and the underlying SWNT directs the polymer self-assembly process. The polymer backbone interchain spacing (d_cc = 1.55 nm) of the outermost layer of adsorbed rrP3HT is approximately 7% larger than is observed for rrP3HT adsorbed on HOPG (d_cc = 1.45 nm). The polymer also wraps around the SWNT at an angle with respect to the SWNT long-axis, which indicates that rrP3HT self-assembly is hierarchical. The conductive polymer´s deposition occurs with epitaxy and is directed by the underlying SWNT chiral structure