Dynamics of Poly(3-hexylthiophene) Monolayers at Solution/Graphite Interfaces

We have studied the dynamics of poly(3-hexylthiophene) (P3HT) monolayers at the interfaces between highly oriented pyrolytic graphite (HOPG) and P3HT solutions in 1,2,4-trichlorobenzene, using scanning tunneling microscopy (STM). Real-time STM observation at room temperature reveals that P3HT molecules adsorbed on graphite are substantially mobile even in densely packed conditions, causing significant fluctuations of the self-organized monolayer of P3HT. We find that in the monolayers, the orientational order is limited to a short range comparable to the polymer chain length. We show that our observations can be understood based on a 2D semiflexible lattice polymer model by performing kinetic Monte Carlo simulations.