Plasma treatment for biomedical application on polymeric substrate

This work arises from the possibility of changing the surface properties of materials with the use of plasma. It proved to be a very good method for treating surfaces, it is in fact able to modify surface properties of materials without altering their bulk properties. In particular, with the Plasma Enhanced Chemical Vapour Deposition (PECVD) is feasible sustaining the polymerization of a specific monomer depositing thin films containing interesting chemical groups. For these reasons, this technique was chosen for modifying polypropylene substrates through the polymerization of acrylic acid, an organic acid carrying the carboxy group (COOH). This chemical group is of particular interest because it has biocompatibility properties itself and can be used for a further grafting reaction allowing further surface modifications. During this works two types of plasma reactor were optimized for obtaining the best working condition, namely, creating a stable coating of poly-acrylic acid resistant to Phosphate Buffer Saline (PBS) and water washing. The physical and chemical properties of the deposited thin films were studied by means of Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR), Water Contact Angle (WCA), XRay Photoelectron Spectroscopy (XPS), Atomic Force Microscope (AFM). The density of COOH groups into the polypropylene surface were evaluated by ion-exchange reaction with Thionin Acetate (THA). A simple model for explaining the particular physical composition and stratification of the films is presented along with a computer simulation. The reactor geometry effect onto the film properties was investigated. Furthermore, some applications of the process were then discussed. Part of the present work consisted in the use of the AFM for internal scopes and extramural collaborations. Among these, the measurement of the thickness of different PEG chains bounded to the plasma treated surface in support of Monte Carlo simulations of their polymer dynamics.