Abstract
As a common inorganic silicon material, nano-SiO2 is extremely hydrophilic due to the presence of a large number of hydroxyl groups on its surface, which limits its application in some fields. In this research, hexadecyltrimethoxysilane (HDTMS) was used to modify nano-SiO2, and the results of water contact angle (WCA), Fourier transform infrared (FTIR), two-dimensional correlation spectroscopy (2D-COS), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM) indicated that the hydrophobic long-chain alkyl of HDTMS was successfully grafted onto the surface of nano-SiO2. When the ratio of nano-SiO2 and HDTMS was 0.25:1, the WCA of nano-SiO2 modified with HDTMS (HDTMS-nano-SiO2) reached 170.9°, which was about 5.62 times higher than that before modification, and the superhydrophobic property was obtained. The novelty of this work lies in the modified nano-SiO2 with a WCA of over 170° and the analysis of the modification mechanism with the help of 2D-COS. This study can provide a reference for the hydrophobic modification of nano-SiO2 and its application field expansion.
Highlights
Nano-SiO2 is nontoxic and odorless with large specific surface area and light weight
The key to preparing a superhydrophobic coating on the substrate surface is to construct the rough structure of binary micro-nano or modify it with low-surface-energy substances to reduce its surface energy.[12−15] As a typical low-surface-energy substance, fluorocarbons have been commonly investigated in hydrophobic modification of such materials.[16−18] Dou et al modified nanoSaniOd2thweitWh C1HA,r1eHac,2hHed,21H30-p.6e°rfl.1u9oLriondeetcayll.tsruicchcoexsysfsuillalynepr(ePpFarDeSd)a, hydrophobic silica gel film with porosity over 90% by the sol−gel method using the hydrophobic fluorocarbon functional group− CF3 as a modified group, which can be used to absorb CO2.20 fluorinated compounds are expensive and may accumulate and become toxic in organisms and the environment.[21,22]
Unmodified nano-SiO2 was so hydrophilic that water drops spread out quickly when hitting its surface, with a water contact angle (WCA) of only 25.8°
Summary
Nano-SiO2 is nontoxic and odorless with large specific surface area and light weight. The glass had a WCA of 139.5° with 0.1% of the modified nanoSiO2.35 Xiong et al synthesized a kind of functional nano-SiO2 with 2,4-dihydroxybenzophenone and HDTMS and introduced it onto the surface of cotton fabric. Because of being widely used for cotton fabric, HDTMS-modified hydrophobic nano-SiO2 probably has potential in other materials and fields. To study this subject, in this paper, we propose to utilize HDTMS as the modifier to modify the surface of nano-SiO2 and to explore the influence of different proportions of reactants on the hydrophobic property of nano-SiO2. The results of this study can provide a reference for the hydrophobic modification of nano-SiO2
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