Comparison of the physicochemical properties and aging behavior of two different APTES-derived plasma polymer-based coatings

Abstract

Recently, new plasma polymerization-based techniques emerged to deposit chemically functional coatings for various applications. However, little is known on the aging of these layers. Therefore, this study aims to investigate the physicochemical properties of aerosol-assisted atmospheric pressure plasma deposited (3-aminopropyl)triethoxysilane-based (AAPD-APTES) coatings and compare their aging behavior to APTES-modified plasma polymerized hexamethyldisiloxane-based coatings (ppHMDSO-APTES). X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle (WCA) and atomic force microscopy (AFM) measurements indicated that the applied power had an insignificant impact on the wettability, chemistry and morphology of the AAPD-APTES films. A complex nitrogen-containing organosilicon layer was obtained with significant preservation of the Si-O-C-bonds. For the ppHMDSO-APTES coatings, XPS indicated that these layers had a significantly higher amount of preserved primary amines and a different surface morphology. Oxidation and hydrolysis of Si-O-C-bonds were the most prevalent aging processes for the AAPD-APTES coatings, while protonation of primary amines was most important for the ppHMDSO-APTES films. This study indicates that further research is needed to examine the differences in coating chemistry and aging of other AAPD-based and conventional plasma polymers. Additionally, it provides a reference to decide which coating type and associated aging processes are preferred for certain applications.