Curing Studies of New Polyimide Model Compounds with Molecular Weights of About 1000 g/MOL

Abstract

Two new polyimide model compounds with molecular weights of ∼1000 g/mol have been synthesized. While the amino terminated compound, 4,4′-bis-N-[N′-(4-aminophenoxy-4′-phenyl)-pyromellitimido]diphenylether,O(PO)2, undergoes a branching or crosslinking side reaction, the corresponding anhydride terminated oligomer N,N′-bis[4(N-(3′,4′-bishydroxycarbonyl)phthal-imido)phenoxy-4′-phenyl]pyromellitimide dianhydride, P(OP)2, loses its anhydride functionality completely upon thermal treatment. In the case of O(PO)2, the formed C=N species can be detected with Raman spectroscopy rather than FT-IR spectroscopy because of its low molecular absorptivity in the infrared region. The formation of imine bonds caused by the attack of terminal amino groups on the imide carbonyl group is evident by the appearance of peaks at about 1665 cm-1 in the Raman spectra. The same behavior can be observed in bulky polyimides blended with an increasing amount of O(PO)2 upon curing.