C. Johnson et Sl. Wunder, FT-RAMAN INVESTIGATION OF THE THERMAL CURING OF PMDA ODA POLYAMIC ACIDS, Journal of polymer science. Part B, Polymer physics, 31(6), 1993, pp. 677-692
The effect of solvent on the curing reactions of PMDA/ODA polyamic aci
ds has been investigated using Fourier transform (FT) -Raman spectrosc
opy. Films of different thicknesses were cured by: (1) doctor blading
15% solids solutions onto glass slides, (2) removing all but the bound
NMP, and (3) removing all the N-methypyrrolidinone (NMP). The rate of
cure and final degree of conversion of the PMDA/ODA polyamic acid to
polyimide increased substantially in the presence of NMP, and this eff
ect was attributed to the plasticizing effect of the solvent. Below a
critical solvent concentration, which was estimated to be approximatel
y 40% of the NMP concentration in the bound-solvent limit, the rate of
imidization slowed down considerably. Comparison of FT-Raman data for
PMDA / ODA polyamic acid: (1) in solution in NMP, (2) complexed with
NMP in the solid state, and (3) in the solid state after all the NMP h
ad been removed with water, indicated that intermolecular interactions
were greatest in the latter case and weakest in solution. Spectra of
PMDA / ODA in NMP solution provide strong evidence for binding of NMP
to the amide carbonyl in solution.