Perfectly Hydrophobic Silicone Nanofiber Coatings: Preparation from Methyltrialkoxysilanes and Use as Water-Collecting Substrate

Abstract

Perfectly hydrophobic (PHO) coatings consisting of silicone nanofibers have been obtained via a solution process using methyltrialkoxysilanes as precursors. On the basis of thermal gravimetry and differential thermal analysis (TG-DTA) and Fourier transform infrared spectroscopy (FTIR) results, the formula of the nanofibers was tentatively given and a possible growth mechanism of the nanofibers was proposed. Because of the low affinity between the coatings and the small water droplet, when using these coatings as substrate for collecting water vapor, the harvesting efficiency could be enhanced as compared with those from bare glass substrate for more than 50% under 25 °C and 60-90% relative humidity. By removing the surface methyl group by heat treatment or ultraviolet (UV) irradiation, the as-prepared perfectly hydrophobic surface can be converted into a superhydrophilic surface.

Hollow polysiloxane nanostructures based on pressure-induced film expansion

“…The developed model especially aims to explain the phase during which the deposited film translates into the nanofilaments. The presented nanostructures are synthesized similarly to previously reported solid SNFs, [12][13][14][15][16][17][18][19][20][21][22][23][24][25] and under scanning electron microscope (SEM), they appear exactly similar, yet detailed transmission electron microscope (TEM) analysis reveals them to exhibit a hollow core. The h-SNFs also differ from the previously reported polysiloxane nanotubes 26 in that h-SNFs are topographically similar to solid SNFs, while the nanotubes exhibit a different morphology.…”

“…12,13 In addition, SNFs have been shown to retain the CassieBaxter wetting state even when subjected under pressure. 9 In 2006-2007, three groups independently reported on the first successful synthesis of the 1D polysiloxane nanostructures [14][15][16] and later more studies emerged to deepen the understanding of the process parameters, 12,13,[17][18][19][20][21][22][23][24][25] and recently, also larger tubular polysiloxane structures were introduced. 26 A few growth models for the SNFs have been proposed until this day.…”

“…26 A few growth models for the SNFs have been proposed until this day. [18][19][20]24,27,28 However, these models are challenged by our observation of hollow polysiloxane nanostructures. Gao and McCarthy 27 were the first to propose a growth mechanism for SNFs, which they synthesized in solution phase from a trimethylchlorosilane/tetrachlorosilane (TMCS/TCS) azeotrope.…”

“…The study suggested a growth mechanism based on initial island growth followed by 'self-assembly' type of ordering due to the amphiphilic nature of hydrolyzed precursor molecules. Chen et al 20 used solution-phase synthesis and determined by differential thermal analysis that the end-product consisted of CH 3 SiO 1·12 (OH) 0·76 , which indicated that ca. three quarters of the end-product polysiloxanes were not cross-linked.…”

One-dimensional silicone nanofilaments

“…Probably, the most outstanding property of these coatings is their extreme water repellency [7][8][9][11][12][13][14] with contact angles up to 180° being measured [7]. Therefore, the investigation of the superhydrophobicity of 1D-SNF coatings either aiming at commercial applications or with respect to the theoretical understanding is the central part of many studies .…”