Chemical structure/mechanical properties of para-aminostyirene (PAS)-terminated telechelic polyimides
Résumé
We have synthesized a difunctional model compound PAS-HFDE-PAS, obtained by condensation between a dianhydride (6-HFDA), hexafluoroisopropylidene-2,2′-bis (phthalic acid anhydride) and two mole equivalents of para-aminostyrene (PAS) amines. It was then characterized using spectroscopic and thermal methods, including a kinetic study of monomer reactivity in the temperature range of 100-300°C. The results enabled us to study and characterize two series of PAS-functionalized polyimides synthesized in the laboratory: phenylenediamine (PAS a polyimide) and cardo diamine (PAS polyimide) based. Thermomechanical data obtained with these polyimides showed the presence of two phase transitions, α and β, associated with vitreous transition and with oscillation of phenylenebenzimide structures around the C(CF3)2 flexible linkage of HFDA. A study of chemical structure (determined by 1H and 19F n.m.r.)/properties correlation study was carried out by determining the effect of molar mass and the type of diamine on the thermomechanical properties of telechelic polyimides before cross-linking. © 1998 Elsevier Science Ltd. All rights reserved.