Swelling and Water Uptake Behavior of Nanofilms Obtained by a Magnetron Enhanced Plasma-Polymerization Process

Abstract

This work deals with the water uptake and swelling behavior of magnetron-enhanced plasma-polymerized nanofilms in an aqueous medium. Those coatings are used in biomedical applications such as implants or contact lenses. The role of water in biomaterial surface science is considered to be of great importance. Water is not only the major molecule in most living organisms (70%) and the carrier of cells but it is also the medium in which biochemical processes take place. Because of its small size and mobility, water is the first molecule to come in contact with a biomaterial in any clinical application.[1] It is believed, that the degree of polymer swelling strongly affects the interaction of proteins with the surface of the polymer, which determines its biocompatibility. Polymers with a high swelling degree show weak enthalpic interactions with proteins, resulting in a protein-repellency.[2] A new approach is applied, which combines three characterization techniques: dynamic contact angle measurements, optical waveguide spectroscopy, and electrochemical impedance spectroscopy. A relation between the composition of the films and the water and salt transport phenomena through the nanofilm was observed. A higher amount of oxygen in the precursor gas ratio in the polymerization process leads to a higher wettability as well as a higher water and salt intrusion. Based on this observation an electrical model was introduced and helped to interpret the experimental results.