Superhydrophobic, photothermal, and UV-resistant coatings obtained by polydimethylsiloxane treating self-healing hydrophobic chitosan-tannic acid surface for oil/water separation

Surface hydrophobicity is generally created by lower surface energy materials. However, it is predictable. Simultaneously, it is rare to construct a self-healing surface hydrophobicity using hydrophilic materials, which is an emerging and significant aspect. Herein, we for the first time fabricated the unpredictable surface hydrophobicity on the cotton fabric surface by utilizing chitosan and tannic acid (labelled as Cot@PTA@PTA-CS), in which chitosan played the decisive role. Interestingly, the surface hydrophobicity of Cot@PTA@PTA-CS could be recovered under the heating treatment. Notably, using the hydrophilic materials realizes the unpredictable surface hydrophobicity with self-healing characteristics, which is an advanced work in contrast to the conventional predictable surface hydrophobicity created by fluorine-free hydrophobic or fluorinated materials. Then, Cot@PTA@PTA-CS was treated with polydimethylsiloxane to obtain surface superhydrophobicity, regarded as Cot@PTA@PTA-CS@PDMS. Cot@PTA@PTA-CS@PDMS and Cot@PTA@PTA-CS all exhibited good hydrophobicity after mechanical abrasion. Moreover, Cot@PTA@PTA-CS@PDMS exhibited good repellency to 95 °C water, diiodomethane, ethylene glycol, and dimethyl sulfoxide. So, the surface free energies of modified cotton fabrics were calculated. Besides, the modified cotton fabrics also possessed excellent UV resistance, anti-oxidation activity, photothermal effect, and self-cleaning. Finally, Cot@PTA@PTA-CS@PDMS was used for the high-efficient oil/water separation. Briefly, this work provides a novel and feasible strategy for creating unpredictable surface hydrophobicity with self-healing performance by chitosan and tannic acid, inspiring more scholars to fabricate hydrophobic surface by hydrophilic materials.