FTIRAS STUDY OF VAPOR-DEPOSITED PYROMELLITIC DIANHYDRIDE AND OXYDIANILINE AND THEIR SOLID-STATE REACTION TO POLYIMIDE ON PT(111)

Condensation and adsorption of pyromellitic dianhydride (PMDA) and 4,4 oxydianiline (ODA) on a platinum (111) single crystal surface was studied by IRAS and X-ray photoemission. Condensation at 225 K results in the formation of amorphous multilayers (ODA) and metastable crystalline multilayers (PMDA). Warming the multilayers to 260 K leads to the formation of crystallites stable up to their sublimation temperature. The IRAS results show that the molecular symmetry of the PMDA molecules in the crystalline phase is altered. For ODA the results show that the crystalline phase has a preferential orientation with respect to the surface plane. In residual monolayer phases PMDA is adsorbed side on to the surface plane, whereas for ODA fragmentation of the molecules is observed. Simultaneous condensation of PMDA and ODA at 220 K leads to a mixed adsorbate phase in which amino groups of the oxydianiline molecule are bound in a reactive environment. Formation of an amine carboxylate salt in the coadsorbed phase is observed at 275 K, polyamic acid (PAA) formation occurs around 375 K and imidization to polyimide starts above 410 K. Ambiguities in the vibrational band assignment for the intermediate reaction products in the solid state reaction are discussed. For comparison we also present the first FTIR data for a polyimide film prepared by Langmuir Blodgett techniques.