Abstract
The interactions between oxidised tantalum and methylene diphenyl diisocyanate (MDI) have been investigated by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Thin (approximately 2 nm) and thick layers of polymeric MDI were deposited on tantalum; one set was cured at 200 degrees C, the other dried at ambient temperature (20 degrees C). The thick layers serve as a characteristic pMDI layer, and thin layers contain information relating to the nature of interfacial bonding. By careful fitting of the N1s region contributions relating to interfacial bonding have been established. All spectra show an N(delta+)contribution indicative of acid-base bonding; in the case of the thick films, this is of an intermolecular nature whereas in the thin films, the more intense contribution is a result of such forces between pMDI and substrate. This is confirmed by ToF-SIMS. A lower binding energy component at ca 396 eV on the air-dried thin layer of pMDI is the result of a formal reaction between pMDI and tantalum yielding a nitride-like species in the N1s spectrum.