Reversible switching between hydrophobicity and oleophobicity of polyelectrolyte-functionalized multiwalled carbon nanotubesvia counterion exchange

Abstract

Poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes were grafted onto the surface of multiwalled carbon nanotubes (MWCNTs) by surface-initiated atom transfer radical polymerization (ATRP). The coating of the PMETAC modified MWCNTs (MWCNT-PMETAC) was prepared on the copper substrate by a spraying method. The wettability transition of the MWCNT-PMETAC surface between superhydrophobicity and hydrophilicity can be easily achieved via counterion exchange. In addition, the MWCNT-PMETAC surface showed an oil contact angle about 138.6 ± 1.4° with a 5 μL hexadecane droplet and exhibited superoleophilicity after proper anions exchange, and this switch was also reversible. The counterion exchange of the MWCNT-PMETAC surface was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle (CA) measurement.