Nanowires of conjugated polymer prepared by tuning the interaction between the solvent and polymer

Abstract

The nanowire of conjugated polymer with higher density is desirable for its improved charge transport. However, at a higher solution concentration, the conjugated polymer chain entanglement is severe and not beneficial for the nucleation to grow nanowires. In this paper, we control the equilibrium of entanglement ↔ disentanglement ↔ nucleation and growth by tuning the radius of interaction (Ra) between the solvent and conjugated polymer. At the critical Ra, the disentangled polymer chain could nucleate to form nanowires because its content is moderately supersaturated. Thus, the equilibrium of entanglement ↔ disentanglement is broken and the entangled polymer chain is further continuously disentangled to provide easier diffusivity of chains for nanowire formation. Accordingly, the dense nanowires of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno-[3,2-b]thiophene] (PBTTT-C14) were formed in the mixed solvent carbon disulfide (CS2): cyclohexylbenzene (ChB) = 3:7 (Ra = 2.56) at a higher concentration of 1 mg/ml by aging. The density of the nanowire increased with increasing concentration and aging time. The nanowires were more than 10 μm in length and about 20 nm in width. The contrast was obvious in transmission electron microscopy which indicated the high electronic density and the high crystallinity of the nanowires.