Molecular-level periodic arrays of long-chain poly (3-hexylthiophene-2,5-diyl) driven by electric field

Abstract

Two-dimensional (2D) periodic arrays of conductive polymers represent an attractive platform for wiring functional molecules into the integrated circuits of molecular electronics. However, the large-scale assembly of polymer periodic arrays at molecular level faces challenges such as curling, twisting, and aggregation. Here, we assembled the periodic arrays of long-chain poly(3-hexylthiophene-2,5-diyl) (P3HT, Mw = 65 k) at the solid-liquid interface by applying the electric field, in which the charged chain segments were aligned. The atomic force microscopy (AFM) imaging revealed that individual P3HT chains assemble into monolayers featuring a face-on orientation, extended chain conformation and isolated packing, which is thermodynamically more stable than folded chains in 2D polycrystals. The assembly process initiates with the formation of disordered clusters and progresses through voltage-dependent nucleation and growth of extended-chain arrays, wherein continuous conformational adjustments along the nucleation pathway exhibit the dependence on the cluster size.