Curing chemistry of phenylethynyl-terminated imide oligomers: Synthesis ofC-13-labeled oligomers and solid-state NMR studies

4-(Phenylethynyl-alpha,beta-C-13)phthalic anhydride (PEPA) and C-13-labeled phenylethynyl-terminated imide (PETI) oligomers were synthesized, and soli d-state C-13 nuclear magnetic resonance (NMR) spectroscopy was used to dete rmine the structure of cured oligomers. Solid-state C-13 NMR spectra were c ollected before and after thermal curing. Using solid-state C-13 NMR differ ence spectroscopy, several cure products were identified. The observed C-13 NMR resonances were assigned to four different classes of cure products: a romatics, products from backbone addition (substituted stilbenes and tetrap henylethanes), polyenes, and cyclobutadiene cyclodimers. The effects of pos tcuring and oligomer chain length on the structure of the cured resins were examined. (C) 2000 John Wiley & Sons, Inc.