Microwave Plasma Reactions of Imidazole on Polyurethane Elastomer Surfaces: A Spectroscopic Study

Recently initiated studies concerning surfacemodifications of poly(dimethylsiloxanes) usingmicrowave plasmonswere extended to polyurethane (PU) surfaces. However,when the same experimental conditions used in the closed and open flowmicrowave plasma reactorswere 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 CdN 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 flow reactor conditions. Quantitative assessments of the surface reactions at various depths are also presented.