MICROWAVE PLASMA REACTIONS OF IMIDAZOLE ON POLY(DIMETHYLSILOXANE) ELASTOMER SURFACES - A SPECTROSCOPIC STUDY

Although there are various forms of energy available for conducting surface and interfacial reactions, microwave energy generated plasmas appears to be an effective source for reacting monomeric molecules to elastomeric surfaces. In this study, closed and open flow microwave plasma reactors were developed and utilized to react imidazole molecules to cross-linked polydimethylsiloxanes (PDMS) surfaces. Using closed reactor, imidazole molecules are chemically bonded on the PDMS surface through hydrogen abstraction of the N-H bonds of imidazole. Their orientation, as determined by polarized ATR FT-IR spectroscopy, appears to be preferentially parallel to the PDMS surface. The amount of imidazole reacted to the PDMS surface increases at discharge pressures not exceeding 53.3 Pa, and discharge-times not exceeding 20 s. Extended discharge times, however, are destructive to chemically attached imidazole molecules to PDMS. In the open flow reactor, imidazole molecules are reacted to the PDMS surface by ring opening of the imidazole entity to form C=N surface species. Both reactivity and the extent of the ring opening reactions can be controlled by the plasma reaction parameters, discharge pressure, and time. The presence of silica microdomains on PDMS surface inhibits imidazole reactions to PDMS.