Study on peculiar carbon pattern formation from polymer blend thin films under electric fields

In this study, we demonstrate the formation of a peculiar carbon pattern from polyacrylonitrile/poly(methyl methacrylate) (PAN/PMMA) blend thin films under external electric fields. When a spin-coated PAN/PMMA blend thin film was exposed to an electric field, the surface of the thin film facing air layer would fluctuate due to the electrohydrodynamic instability phenomenon induced by an electrostatic force. At the same time, the interface between PAN and PMMA would also become unstable because of the difference in the dielectric constants of PAN and PMMA. The microstructure of the PAN/PMMA thin film obtained after field exposure was influenced by the combined effect of the two phenomena. Subsequent controlled thermal treatment produced an unprecedented and peculiar carbon pattern, which remained intact during carbonization. The effect of experimental parameters such as field intensity, exposure time, and film thickness on the microstructure of the polymer precursor and resulting carbon pattern was investigated. This work provides a strategy to obtain carbon structures showing specific surface texture and certain properties that have been inaccessible by any other means.