Plasma polymerized 2-ethyl-2-oxazoline: Chemical characterization and study of the reactivity towards different chemical groups

Poly(2-ethyl-2-oxazoline) thin coatings were deposited on different substrates by means of low pressure plasma polymerization. The stability of the thin films was evaluated by immersion in different aqueous environments (Phosphate Buffer Saline (PBS) at 37 °C, sodium dodecyl sulfate (SDS) solutions, aqueous solutions with different pH) and was found to be dependent on the deposition conditions. Chemical characterization of the coatings deposited with different process parameters was performed by means of Attenuated Total Reflectance Fourier Transform Infrared (FTIR/ATR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy. Partial retention of the oxazoline ring was assessed also for the stable coatings. Noteworthy, the coatings displayed an intrinsic fluorescence with an emission maximum around 534–542 nm. The reactivity of the plasma deposited coatings towards carboxylic, amino- and hydroxyl groups was investigated through selected reactions with poly(acrylic acid), amino-terminated polyethylene glycol and zonyl FSO-100 fluorosurfactant. Results indicate strong reactivity with COOH groups, probably as a consequence of the partial retention of the oxazoline ring. As a result, it is suggested that stable coatings can be exploited for the covalent immobilization of COOH-containing proteins or biomolecules, opening a wide range of potential applications.