Abstract: Plasma surface modification can improve biocompatibility and biofunctionality between the physiological environment and the biomaterial surface without changing the material's bulk properties. This dissertation is therefore focused on modifying Dow Cyclotene surfaces through plasma treatment to improve biocompatibility, and on determining and correlating changes in physical and chemical states of the Cyclotene surface to plasma process parameters. The primary goals of this research are to explore the capabilities and limitations of utilizing a dry plasma one-step technique for aminating Dow Cyclotene as a function of four processing parameters (power, pressure, temperature and time), and to develop fundamentally-based models describing the surface amination behavior to provide insight about the reaction mechanisms of the plasma surface modification. The effects of the four processing parameters on the extent of nitrogen incorporation into polymer surface were studied. X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infra-red Spectroscopy-Attenuated Total Reflection (FTIR-ATR), and Atomic Force Microscopy (AFM) were used to characterize the surface chemistry and topography structures. ATR and XPS results showed that nitrogen-containing functional groups were introduced onto the polymer surface through ammonia plasma treatment. The N/C ratio on the surface reached a maximum of 0.24 under the high level intensity plasma conditions accompanied with argon plasma pretreatments. Covalent coupling of oxidized dextran to aminated Cyclotene surface was subsequently realized, as indicated by the outcomes of cell adhesion and spreading studies in which dextran-coated aminated Cyclotene surfaces exhibited significantly reduced cell adhesion and spreading compared with untreated Cyclotene surfaces. Cell adhesion reduction correlated with ammonia plasma treatment conditions and N/C ratio. The chemical stability of plasma modified surfaces is poor, and surface restructuring typically leads to an effective decrease over time of the treatment effects. Therefore an aging study was performed in three different storage environments; the study indicated that the surface modification effect, including both N/C ratio and amino selectivity (NH₂ /N), degraded with storage time and was dependent on the storage media. Finally, a plasma chemistry model in the gas phase and an amination model on a surface were proposed, and the two descriptive models were evaluated using experimental data.