FTIR INVESTIGATION OF CROSS-LINKING AND ISOMERIZATION-REACTIONS OF ACETYLENE-TERMINATED POLYIMIDE AND POLYISOIMIDE OLIGOMERS

The interrelationship between the cross-linking and isoimide-imide iso merization reactions of oligomeric isoimides and imides was investigat ed using FTIR spectroscopy. It was found that cross-linking of the ace tylene units of Thermid IP-600 retarded the local rearrangement of the isoimide to imide conversion of Thermid IP-600 compared with an anili ne-terminated analog, decreasing the rate constant by a factor of abou t 2. The increased flexibility of both the isoimide (Thermid IP-600) a nd imide (Thermid FA-700) oligomers increased the cross-linking rate o f the acetylene end groups by a factor of 4 and 2, respectively, over that of the more rigid imide oligomer (MC-600). With increasing conver sion of the isoimide to imide linkages in Thermid IP-600, the kinetic parameters, E(a) and ln A, for the cross-linking reaction of this olig omer became the same as those for the oligomeric imide, Thermid MC-600 . (c) 1994 John Wiley & Sons, Inc.