Recently initiated studies concerning surface modifications of poly(dimethylsiloxanes) using microwave plasmons were extended to polyurethane (PU) surfaces. However, when the same experimental conditions used in the closed and open flow microwave plasma reactors were applied, no chemical bonding of imidazole molecules to PU surfaces was detected. In order to facilitate the imidazole-urethane surface reactions, PU specimens were immersed in an imidazole-containing methylene chloride solution and exposed to Ar microwave plasmons. This approach appears to be successful in creating chemically stable imidazole species attached to PU surfaces. Imidazole molecules are bonded to PU surfaces through the C=N bond opening of imidazole, to create C-O-C surface bonds. Analysis of the imidazole-urethane linkages was accomplished using attenuated total reflectance Fourier transform infrared spectroscopy and revealed that the same surface structures on PU surfaces, but different concentration levels of imidazole at various depths from the surface, can be generated under closed and open now reactor conditions. Quantitative assessments of the surface reactions at various depths are also presented.