Rr. Cheng et Sl. Wunder, NMR AND FTIR INVESTIGATION OF THE SOLUTION IMIDIZATION KINETICS OF MODEL COMPOUNDS OF PMDA ODA POLYAMIC ETHYL-ESTER/, Journal of polymer science. Part B, Polymer physics, 34(3), 1996, pp. 435-448
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.