Akademik Veri Yönetim Sistemi
Applied Clay Science, cilt.287, 2026 (SCI-Expanded, Scopus)
In this study, halloysite nanotubes (HNTs) were chemically modified using alkoxysilanes with different alkyl chain lengths, namely methyltriethoxysilane (METES), octyltriethoxysilane (OTES), and hexadecyltrimethoxysilane (HDTMS), synthesized in an ethanol-assisted supercritical CO₂ (scCO₂) medium via a sol–gel process (125 bar, 35 °C). The modified HNTs were used to develop chain-length-controlled clay mineral-based hybrid nanomaterials, which were subsequently deposited as thin films on glass substrates using a modified CO₂-drainage approach. FTIR, XRD, TGA, and XPS analyses confirmed successful silane grafting and the chemical modification of the HNT surface. SEM–EDS and AFM analyses revealed that increasing alkyl chain length resulted in thicker organic layers, higher surface roughness, and more compact hybrid structures due to enhanced surface coverage of HNTs. As a direct consequence of these structural changes, the surface wettability systematically evolved from moderately hydrophilic to highly hydrophobic behavior, with water contact angles increasing from 95° for METES-HNT to 136° and 145° for OTES- and HDTMS-HNT systems, respectively. Mechanical durability tests demonstrated strong interfacial adhesion and structural stability of the HNT-based hybrid films, with RMS roughness decreasing by 15–53% and water contact angles decreasing by only 3–9% after tape-peeling tests. Pencil hardness measurements further indicated that HDTMS-HNT coatings exhibited the highest mechanical integrity. Overall, this study demonstrates a green and scalable scCO₂-assisted strategy for the controlled chemical modification of HNTs and the fabrication of mechanically robust, hydrophobic clay mineral–based hybrid coatings. The combined thermal, compositional, and wettability results provide experimental evidence that alkoxysilane alkyl chain length plays a decisive role in governing siloxane network formation, surface energetics, and durability of HNT-derived hybrid thin films. Importantly, by systematically varying the alkoxysilane alkyl chain length under identical scCO₂ processing conditions, this study establishes a clear structure–property relationship between silane molecular architecture and the resulting microstructural, wetting, and mechanical behavior of scCO₂-derived HNT hybrid thin films, providing new insight for the rational design of durable clay-based functional coatings.