Structure/properties relationship of nadimide-terminated fluorinated polyimides. II. New thermostable systems

• Published in: Polymer international 1997-12, Vol.44 (4), p.435-447
• Main Authors: Grenier-Loustalot, M F, Billon, L, Louartani, A, Bounor-Legare, V, Mison, P, Senneron, M, Sillion, B
• Format: Article
• Language: English
• ISSN: 0959-8103

We have established the chemical structure/mechanical properties relationships of new nadimide-terminated polyimides. Initially, the prepolymers were synthesized by polycondensation of nadic anhydride (NA), hexafluoroisopropylidene-2,2-bis(phthalic acid anhydride) (6HFDA) and to phenylene diamines, meta (mPDA) and para (pPDA) in N-methylpyrrolidone (NMP). After characterizing the microstructure and composition of these systems using chromatographic (HPLC, SEC) and spectroscopic techniques ( exp 1 H and exp 13 C NMR), we determined their thermomechanical properties. The rheology curves obtained showed the presence of two transitions, alpha and beta , associated with the glass transition and a second, sub-vitreous transition, because of local molecular movements. By studying the relationship between chemical structures and mechanical properties, we have shown the influence of endo/exo isomerization of nadimide extremities on the glass transition temperature T sub g . In a given polymer, the value of T sub g increases with increasing percentage of exo isomers.