CONFIRMATION OF THE PRESENCE OF IMINE BONDS IN THERMALLY CURED POLYIMIDES

Model compounds for imines formed during the thermal curing of short c hain polyimides have been synthesized and characterized. These compoun ds have imine bonds (C = N ) formed by the nucleophilic attack of prim ary amines on imide carbonyls. The C = N stretching mode appears at 16 49-1664 cm-1 in the Raman and infrared spectra of these compounds and the band assigned to the carbonyl mode in an imide ring with an imine bond appears near 1740 cm-1. These compounds have been prepared and ch aracterized to verify the conclusions of a previously reported study i n which bands observed in thermally cured short chain polyimides at 16 56 and 1742 cm-1 were assigned as the C = N and associated C = 0 modes , respectively. It has also been confirmed that the C = N stretching m ode in the imide model compounds is inherently IR weak and can only be seen if the concentration of imine species is high. (C) 1993 John Wil ey & Sons, Inc.