The method for the preparation of organic thin films (TFs) is significant due to its attractive potential applications in various devices such as photovoltaic cells, transistors and sensors. However, the conventional preparation methods are expensive and time-consuming. Besides, it is difficult to control the shape and the thickness of the film. In this study, a facile and general bipolar electrolytic micelle disruption (BEMD) approach was firstly established to fabricate a variety of gradient and circular TFs,¹ benefiting from the in situ generated controllable potential distribution on a bipolar electrode (BPE).²

The micellar electrolytic solution was prepared by the addition of organic compound to an aqueous micellar solution containing electroactive surfactant of (11-ferrocenylundecyl)trimethylammonium bromide (FTMA) or α-(11-ferrocenylundecyl)-ω-hydroxypoly(oxyethylene) (FPEG), and lithium sulfate (Li₂SO₄).³ The prepared electrolyte was used for bipolar electrolysis under different conditions.

A polymerizable monomer of N-vinylcarbazole (NVC) was solubilized in micelles composed of a cationic surfactant of FTMA, while copper phthalocyanine (CuPc) and aggregation-induced emission (AIE) compounds were dispersed in micelles constructed from a nonionic surfactant of FPEG. Here, a U-shaped bipolar electrolytic setup generated a sigmoidal potential distribution on the BPE, while a cylindrical bipolar electrolytic setup provided a site-selective potential feature on the BPE. When the micelles composed of electroactive surfactants moved to the BPE surface, the structure of micelles was disrupted selectively on the BPE surface with the oxidation of surfactants. In this process, various organic compounds incorporated into micelles were released on the localized area of the BPE, following the potential distribution. Finally, a variety of gradient and patterned organic thin films formed on the BPE surface. The gradient feature was characterized by UV–Vis analysis, thickness measurement and surface morphology analysis. Besides, modulation of the voltage applied to the driving electrodes or electrolytic solution allowed control of the film thickness.

References:

1. Y. Zhou, N. Shida, I. Tomita, S. Inagi, Angew. Chem. Int. Ed., 60, 14620 (2021).
2. N. Shida, Y. Zhou, S. Inagi, Acc. Chem. Res., 52, 2598 (2019).
3. T. Saji, K. Hoshino, Y. Ishii, M. Goto, J. Am. Chem. Soc., 113, 450 (1991).