Development of superamphiphobic alumina nanofiber mats using trimethoxysilane with a short perfluoroalkyl chain

Abstract

To avoid the generation of hazardous, long-chain perfluoroalkyl carboxylic acids (C _n F_{2 n +1}COOH, n ≥ 7), we develop relatively safer superamphiphobic alumina nanofiber mats. Our fabrication process focuses on two principles: lowering the surface energy using trimethoxy(1H, 1H, 2H, 2H-nonafluorohexyl)silane (C₄F₉CH₂CH₂Si(OCH₃)₃), which has short-chain perfluoroalkyls that are relatively safer than long-chain ones; and creating a high-roughness surface from electrospun alumina nanofibers with an average fiber diameter of 155 nm and inter-fiber spacing of 451 nm. Such mats exhibit super-repellency for water (contact angle ${\theta }^{*}$  = 157°, contact angle hysteresis $\Delta {\theta }^{*}=2^{\circ }$ , advancing angle ${\theta }_{\mathrm{adv}}^{*}=$ 158°, receding angle ${\theta }_{\mathrm{rec}}^{*}=$ 156°), and n-hexadecane ( ${\theta }^{*}$  = 151°, $\Delta {\theta }^{*}=$ 9°, ${\theta }_{\mathrm{adv}}^{*}=$ 152°, ${\theta }_{\mathrm{rec}}^{*}=$ 143°). Furthermore, superamphiphobicity is maintained up to 350℃.