Facile fabrication of biomimetic superoleophobic composite coating

Inspired by the defects of superoleophobic surface with poor friction resistance and the complicated preparation method, bio-dopamine was utilised and the friction-durable superoleophobic composite coating was successfully obtained via Schiff base reaction and self-assembly.

Oil drops as symbolic image.

Dopamine contains the phenolic hydroxyl groups that can react with an amine group or a thiol group. Polydopamine is formed via dopamine self-polymerisation under aerobic and weakly alkaline conditions. Additionally, polydopamine can adhere to the surface of virtually all materials.
First, the self-polymerisation of folic acid induced dopamine to form polydopamine micro-nanoparticles under weakly alkaline conditions. Second, 3,5-Bis(trifluoromethyl)aniline reacted with the phenolic hydroxyl groups of polydopamine nanoparticles via Schiff base reaction. Ammonium hexafluorosilicate was adsorbed on the surface of polydopamine microspheres via electrostatic interactions.

Superoleophobic composite coating applied to cotton fabric

Then, the self-assembly behavior of fs-81 and fs-63 with ammonium hexafluorosilicate occurred on polydopamine nanoparticles via electrostatic interactions. Accordingly, the surface roughness was further increased, for which the limitation of traditional methods of using additional nanoparticles to construct hierarchical rough surface was broken.
Eventually, the superoleophobic composite coating was applied to the surface of cotton fabric. The results showed that the contact angles of the cotton fabric surface with edible oil, ethylene glycol and glycerol were greater than 150° in the air, respectively, after two cycles of self-assembly modification. The contact angles between the cotton fabric surface and edible oil droplets were still greater than 150°after 25 mechanical abrasion cycles. In addition, the surface free energy of cotton fabric was decreased by 64.1 % after finishing the coating.

The study has been published in Progress in Organic Coatings Volume 142, May 2020.

Image source: Pixabay.

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