Custom-Designed Carbosilane-Based Reactive Surfactants for Surface Hydrophobization─AFM, Raman Microscopy, and XPS Investigations

Abstract

The reactive carbosilane cationic surfactant (SK) has been studied for glass surface hydrophobization by blending with oligodimethylsiloxane derivatives, comprising epoxide (EO) and amine/alkoxyl motifs (AO), and deposition using three different approaches: spray, spin, and dip coating. Our contribution comprises the synthesis and structure characterization of a surfactant (1H NMR, FT-IR and Raman spectroscopies), the optimization studies for the layer deposition by tuning the chosen parameters and compositions, as well as the determination of contact angles and surface energies. The crucial roles of the layer composition and the deposition methodology were carefully investigated, especially in terms of the reactivity of SK with siloxane derivatives and glass surfaces. The experiments were supported by the calculation of solubility parameters (δ) and the dispersion (δD), polar (δP), and hydrogen bonding (δH, including its splitting into donor (δHD) and acceptor (δHA) counterparts) components utilizing HSPiP software, showing the possibility of appropriate component blending. The layer structure and morphology were studied via atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analyses with Ar+ sputtering as well as in-depth Raman microscopy. It was demonstrated that spray coating was an inappropriate method since it provided an extremely rough layer, while dip coating provided a deposit of limited stability due to the presence of separated SK deposits. The optimal system comprised SK combined with AO by a spin-coating approach, enabling both surface hydrophobization and the formation of a stable, chemically attached layer on the glass surface.