Superhydrophilic surfaces are known to exhibit extreme oil repellency under water. However, once the surface is fouled by oil, it is difficult to recover its superhydrophilicity. Another challenge is how to scalable manufacture coatings that can be applied onto various surface. Here, we create a robust superhydrophilic coating that repels oil under water by grafting hygroscopic poly(acrylic acid) (PAA) on SiO<sub>2</sub> nanochains, followed by spray coating them onto substrates, leading to the formation of a porous membrane with nanoscale roughness and large porosity. We show that both the morphology of the nanoparticle assembly and the surface chemistry of PAA are necessary to enable robust superhydrophilicity (water contact angle ≈ 0°) and underwater superoleophobicity (oil contact angle underwater ≥ 165°). PAA-grafted nanochain assembly exhibits extremely low contact angle hysteresis (&lt; 1°) and small adhesion hysteresis (≈ 0.2 mN/m), where oil can readily roll off from the surface. More interestingly, we find that even after the PAA grafted nanochain coating is purposely impregnated with oil, oil can be readily lift up and completely detached from the coating within 10 seconds when placed under water, recovering the superhydrophilicity and underwater superoleophobicity of the coating.

Underwater, anti-oil fouling coatings from spray coating of polymer grafted silica nanochains

256th National Meeting (2018)

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