Spatially Ordered Poly(3-hexylthiophene) Fibril Nanostructures via Controlled Evaporative Self-Assembly

Hierarchically structured, gradient concentric rings of regioregular conjugated polymer, rr-poly(3-hexylthiophene) (rr-P3HT) with randomly or directionally crystallized nanofibrils over large areas are obtained by regulating consecutive “stick-slip” motions of the three-phase contact line in a confined geometry consisting of an upper curved sphere surface and a lower flat Si substrate (i.e., sphere-on-flat geometry), which leads to an axially symmetric capillary-bridge (bound solution). Self-organized concentric P3HT ring patterns result from mediating intermolecular interactions between the polymer molecules, and varying the solvent concentration. More interestingly, from the lower solution concentration “shish-kebab” like morphologies are observed in between adjacent rings. These unusual, directionally crystallized structures are formed spontaneously parallel to the moving direction of the contact line on solvent evaporation. Subsequently, I–V characteristics of the directionally crystallized and randomly distributed P3HT nanofibrils formed across the electrodes are investigated and compared.