NMR AND FTIR INVESTIGATION OF THE SOLUTION IMIDIZATION KINETICS OF MODEL COMPOUNDS OF PMDA ODA POLYAMIC ETHYL-ESTER/

Meta- and para-diethyl-p,p-oxydiphenylene pyromellitamide (DOP), the m odel compounds of the meta and para PMDA/ODA polyamic ethyl ester, wer e synthesized and characterized by NMR and FTIR spectroscopy. Investig ation of the imidization in d(6)-DMSO solution using NMR and FTIR tech niques has shown that both the half imide and imide were formed. Quant itative analysis of the curing rates and degrees of conversion of the isomers in dilute d(6)-DMSO solution as a function of time under isoth ermal conditions or as function of temperature at fixed time (1 h) ind icated that the kinetics of the ring closure reaction of the meta and para isomers were the same within 10%. This suggests that intrinsic re activity differences between the isomers do not have much effect on th e imidization process and do not account for the differences in rate t hat have been observed for the meta and para polymers in the solid sta te. No interconversion between the two isomeric forms occurred below 1 80 degrees C, as has been observed for polyamic acids and their model compounds. The degree of conversion strongly depended on the reaction temperature and increased quickly after 170 degrees C. The rate consta nt of the second ring closure reaction was found to be approximately t hree to four times the rate constant of the first ring closure reactio n. (C) 1996 John Wiley & Sons, Inc.