An approach to avoid degrafting of hydrophilic polymers in aqueous environment

Abstract

Hydrophilic adaptive polymer coatings, such as poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) films, are characterized by high hydrophilicity and swelling, which is caused by unique interactions with water molecules based on their molecular structure. This specific behavior allows for the discussion of various potential applications, including easy-to-clean, protein resistance, anti-fouling or anti-fog properties. However, a major drawback in the implementation of these coatings is their stability in aqueous environments, which is a common limitation of hydrophilic polymer films, even when they are chemically grafted to the substrate. In this study, SiO₂ model surfaces were used to demonstrate that it is feasible to markedly enhance the water stability of thin grafted poly(MPC) films while preserving their functionality subsequent to water treatment. To this end, a set of three copolymers of MPC with varying amounts of glycidyl methacrylate (GMA) were synthesized, in which GMA serves the dual role of crosslinker and coupling agent. The impact of copolymer composition and grafting time on film stability was examined through the implementation of water performance tests in combination with spectroscopic in situ ellipsometry measurements. The optimization of polymer composition and grafting time resulted in the development of polymer layers that exhibited stability for a minimum of 100 days in water at room temperature and for 24 h in boiling water. The optimized films retained their easy-to-clean properties subsequent to the water performance tests.