Jr. Ojeda et al., PHYSICAL AND CHEMICAL EVOLUTION OF PMDA-ODA DURING THERMAL IMIDIZATION, Journal of polymer science. Part B, Polymer physics, 33(4), 1995, pp. 559-569
The processing of poly(imide) films from poly(amic acid) solutions inv
olves the simultaneous loss of solvent and chemical conversion, and ma
y involve structural reorganization such as orientation or crystalliza
tion. Here, we describe weight loss, solvent sorption. Fourier transfo
rm infrared (FTIR), and wide-angle x-ray scattering (WAXS) studies dur
ing thermal imidization of the commercially important poly(imide) PMDA
-ODA. The results indicate that imidization proceeds nearly to complet
ion before significant crystallization occurs. The experimental data a
re interpreted in terms of a triangular phase diagram that makes it po
ssible to plot the processing pathway during the conversion from poly(
amic acid) solution to solid poly(imide). In constructing this triangu
lar phase diagram the extent of imidization (i.e., the composition of
the poly(amic acid-co-imide) copolymers during conversion) is treated
as an independent thermodynamic variable. The form of the triangular p
hase diagram can be predicted from the Flory-Huggins lattice theory of
mixing. There is inevitably a two-phase region present due to the rel
atively poor solubility of the poly(imide) in the poly(amic acid) solv
ent (NMP). The specific processing pathway taken depends on the relati
ve amount of solvent loss and imidization during conversion. Further d
etails about the triangular phase diagrams of poly(imides) will requir
e such studies as solvent swelling at intermediate stages of conversio
n. (C) 1995 John Wiley and Sons, Inc.