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

Abstract

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.