Plasma Surface-modification Of Medical Polymers For Enhancing Anti-infective Properties

Medical polymers are used widely in medical fields because of their excellent mechanical properties and moderate biocompatibility. However, their bacterial infection is a life threatening complication and can lead to significant morbidity and mortality. Therefore, this thesis is focused on enhancing anti-infective properties of medical polymers by novel plasma surface-modification. Polyethylene (PE) and poly vinyl chloride (PVC) as examples are surface-modified by two methods involving plasma grafting and plasma implantation, so as to endow excellent anti-infective properties to their surfaces. Consequently, plasma immersion ion implantation (PIII) is demonstrated to be a viable approach to achieve anti-infective performances of medical polymers.Influences of O₂ and H₂O plasma-modification with variable parameters on physical and chemical properties of samples'surface are investigated to understand interaction between plasma and polymer's surface. XPS, AFM, contact angle instrument etc. are employed to analyze physical and chemical properties of the modified surface. Experimental results indicate that there are plenty of oxygen containing functional groups occurring on PE and PVC surfaces due to O₂ and H₂O plasma modification. Moreover, these surface-modifications make their surface macromolecule take dehydrogenation and dechlorination, and also have little effect on surface morphology. Comparing by two plasma-modifications, it is found that O₂ plasma is better suitable for improving surface hydrophilicity and the quantity of oxygen than H₂O plasma.Both PE and PVC surfaces are plasma-grafted with antibacterial agents involving triclosan and bronopol under the optimal parameters. Amount of grafting antibacterial agents and physical and chemical properties are discussed in detail, and the co-relation between samples surface and bacterial behaviors is studied as well. Results demonstrate that antibacterial agent grafting PE and PVC have excellent antibacterial effects on E. coli and S. aureus, more than 90%, and they can inhibit the bacterial adhesion on their surface. Meanwhile, when plasma modification factors are variable, including kinds of plasma, antibacterial agents and medical polymers, antibacterial performances and physical and chemical properties are researched profoundly. Results prove that Ar plasma-grafting triclosan PE surface has the optimal antibacterial performances at -4kV,30min.Plasma immersion ion implantation is employed to implant Cu or Ag plasma into PE sample for enhancing antibacterial properties. Under low energy plasma, Cu or Ag plasma is located at the range of several hundred nanometers. It is observed that implanted Cu or Ag is in zero state among the molecule, and little amount on surface and large amount of Cu or Ag in inner can provide PE sample immediate and long term antibacterial performances. O₂,NH₃ and N₂ plasma co-implantation are respectively conducted to modify chemical functional groups on the macromolecule, and these groups can adjust the releasing rate of Cu and Ag for a long term antibacterial properties. It is found that co-implanted N₂ plasma has better control on the releasing rate of Cu and Ag than other gas plasmas.