[Langmuir] Nanotexturing of Conjugated Polymers via One-step Maskless Oxygen Plasma Etching for Enha
A one-step maskless oxygen plasma etching process is investigated to nanopattern conjugated polymer, dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)), and to examine the effects of nanostructures on the inherent tunable wettability of the surface and the droplet mobility. Etching characteristics such as the geometry and dimension of the nanostructures are systematically examined for the etching power and duration. The mechanism of self-formation of vertically-aligned dense-array pillared nanostructures in the one-step maskless oxygen plasma etching process is also investigated. Results show that the lateral dimensions such as periodicity and diameter of the pillared nanostructures are insensitive to the etching power and duration, whereas the length and aspect ratio of the nanostructures increase with them. X-ray photoelectron spectroscopy analysis and thermal treatment of the polymer reveal that the co-deposition of impurities on the surface resulted from the holding substrate is the primary reason for the self-formation of nanostructures during the oxygen plasma etching, while the local crystallinity subject to thermal treatment has minor effect on the lateral dimensions. Retaining the tunable wettability (oleophobicity) for organic droplets during the electrochemical redox (i.e., reduction and oxidization) process, the nanotextured PPy(DBS) surface shows significant enhancement of the droplet mobility, compared to the flat PPy(DBS) surface with no nanotextures, by making the surface superoleophobic (i.e., in a Cassie-Baxter wetting state). Such enhancement of the tunable oleophobicity and droplet mobility of the conjugated polymer will be of great significance in many applications such as microfluidics, lab-on-a-chip devices, and water/oil treatment.
Youhua Jiang, Jian Xu, Junghoon Lee, Ke Du, Eui-Hyeok Yang, Myoung-Woon Moon, and Chang-Hwan Choi Langmuir, Just Accepted Manuscript DOI: 10.1021/acs.langmuir.7b01593 Publication Date (Web): June 15, 2017 Copyright © 2017 American Chemical Society