Abstract
Cellulose nanofibrils (CNFs) have attracted much attention because of their renewability and potential biocompatibility. However, CNFs are extremely hydrophilic due to the presence of a large number of hydroxyl groups, limiting their use as a water-resistant material. In this work, we controlled the adsorption behavior of silica nanoparticles on the surface of CNFs by adjusting the synthesis conditions. The silica nanoparticle size and packing efficiency on the CNF surface could be controlled by varying the ammonium hydroxide and water concentrations. In addition, hexadecyltrimethoxysilane (HDTMS) was successfully grafted onto CNF or CNF/silica nanocomposite surfaces, and the quantitative content of organic/inorganic substances in HDTMS was analyzed through XPS and TGA. The HDTMS-modified CNF/silica nanocomposites were more advantageous in terms of hydrophobicity than the HDTMS-modified CNF composites. This is because the silica nanoparticles were adsorbed on the surface of the CNFs, increasing the surface roughness and simultaneously increasing the amount of HDTMS. As a result, the HDTMS-modified CNFs showed a water contact angle (WCA) of ~80°, whereas HDTMS-modified CNF/silica nanocomposites obtained superhydrophobicity, with a WCA of up to ~159°. This study can provide a reference for the expansion of recyclable eco-friendly coating materials via the adsorption of silica nanoparticles and hydrophobic modification of CNF materials.
Highlights
Received: 21 January 2022Environmental issues due to plastics are increasing the demand to replace petroleumbased materials with eco-friendly natural materials
The size of the silica nanoparticles was determined via the transmission electron microscopy (TEM) image analysis and the Zetasizer analysis, and the silica content was determined via thermogravimetric analysis (TGA)
In the cellulose nanofibrils (CNFs)/silica-1, it was confirmed that anisotropic silica nanoparticles with a size of around 10–30 nm were adsorbed on the CNF surface (Figure 2a,b)
Summary
Received: 21 January 2022Environmental issues due to plastics are increasing the demand to replace petroleumbased materials with eco-friendly natural materials. The various types of nanocellulose can be classified according to their width and length; these include cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and cellulose microfibrils (CMFs) [3,6]. CNCs have a short, rod-like shape around 2–20 nm in width and around 100–500 nm in length [7]. The modification is mainly based on the reactivity of the hydroxyl group for surface and structural properties. It is through functionalization reactions—such as oxidation, etherification, esterification, silylation, and polymer grafting—that nanocellulose can improve its extraction capacity and enhance the hydrophobicity of its surface [7,14,15]
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