Recognizing the function of different silane coupling agents on MXene adsorption/barrier behavior in solvent-borne epoxy coatings: Experimental studies, density functional theory, and molecular dynamics simulations

Two different silane agents including 3-aminopropyltriethoxysiane and tetraethyl orthosilicate are used to achieve MXene nanosheets grafted with amino-silane (Silane@MXene) and MXene nanosheets covered with SiO 2 nanoparticles (SiO 2 @MXene), respectively. The Silane@MXene and SiO 2 @MXene are used as nanofillers in a solvent-based epoxy coating and applied with a dry film thickness of 200 ± 50 μm on steel substrates. The neat epoxy and epoxy loaded with SiO 2 @MXene and Silane@MXene show water contact angles of 75.8°, 88.4°, and 115.8° and adhesion strengths of 3.2, 4.8, and 6 MPa, respectively. The neat sample fails after 28 days of immersion in the 3.5 wt% NaCl solution, while the coatings loaded with SiO 2 @MXene and Silane@MXene show low frequency impedance modulus of 4.34 × 10 7 and 2.97 × 10 8  Ω.cm 2 after 56 days of immersion, respectively. Moreover, density functional theory calculations indicate that both APTES and TEOS structures exhibit reactivity and promise for interacting with the MXene/solution interface. Molecular dynamics simulation shows that both Silane@MXene and SiO 2 @MXene are effective in protecting against the 3.5 wt% NaCl solution. The diffusion of Na + and Cl − in Silane@MXene is marginally higher compared to the SiO 2 @MXene systems. The exceptional adsorption capacity of the Silane@MXene makes it a suitable material for protection against NaCl solution.