83 / 2021-06-14 14:05:24

BIOINSPIRED STRUCTURES FOR TUNING SURFACE WETTABILITY WITH CELLULOSIC MATERIALS

wettability, nanocellulose, structure, stability, tunability

Materials with different wettability surfaces (including super-hydrophobic, super-oleophobic, super-hydrophilic, super-lipophilic, etc.) potentially applied in self-cleaning, anti-fogging, anti-fouling, anti-corrosion, oil-water separation and microfluidic equipment have received extensive attention from academia and industry. The wettability of materials is governed by chemical composition and the hierarchical structure of the surface and Wenzel and Cassie-Baxter models have indicated that the surface roughness can enhance the wettability of the solid surface¹. Super-hydrophobic surface (Water Contact Angle＞150^o) can be obtained by tailoring the surface structures of hydrophobic materials by increasing roughness, as superhydrophobic and self-cleaning lotus leaf surface shows. Inspired by the abovementioned related researches, we used hydrophobic nanocellulose prepared by mechanochemical esterification with hexanoyl chloride as our previous work² reported to construct various hydrophobic surfaces. The hydrophobic nanocellulose with Water Contact Angle 83.4^o can stably disperse in tetrahydrofuran and N, N-dimethylformamide while aggregating in strong polar solvents such as water. Accordingly, sizes of the hydrophobic nanocellulose aggregates can be tailored by introducing various amount of water in the intense stirring process, and the dispersion of hydrophobic nanocellulose became turbid at the same time. Then the mixtures were dropped onto the glass and dried at different temperatures and humidity. With the amount of water increasing, the dispersion became more turbid and higher Water Contact Angle of surfaces were obtained and humidity has the same effect on hydrophobicity while temperature has little effect. Finally, polydimethylsiloxane commonly used as binder was applied to improve the mechanical durability of the hydrophobic coating. As a result, surfaces with tunable wettability and stability were obtained through the facile methods. This work not only provides an inspiration for using cellulose-based materials to prepare surfaces with special wettability, but also expands the application of cellulosic materials in different fields.