Synthesis of benzylidene‐pendant polyphthalimidines from flexible bisphthalides and various diamines

Abstract

AbstractNew polyphthalimidine‐forming monomers, 5,5′‐(oxydi‐p‐phenylenedicarbonyl)bis(3‐benzylidenephthalide) and the 6,6′‐derivative, were synthesized by the Friedel–Crafts reaction of diphenyl ether with 5‐ and 6‐chloroformyl‐3‐benzylidenephthalide, respectively. The direct polycondensation of these bisphthalides with both aliphatic and aromatic diamines in o‐phenylphenol at 200–250°C afforded polyphthalimidines having inherent viscosities of 0.2–1.2 dL/g in almost quantitative yields. Syntheses of aliphatic polyphthalimidines with higher inherent viscosities were also achieved by a two‐step procedure involving ring‐opening polyaddition and subsequent thermal cyclodehydration. All the polymers were amorphous and readily soluble in N‐methyl‐2‐pyrrolidone (NMP), m‐cresol, nitrobenzene, pyridine, and chloroform. Tough and flexible films could be cast from NMP solutions of the polymers. Glass transition temperatures of the polyphthalimidines were in the range of 158–246°C. The thermogravimetry of the aromatic polymers showed 10% weight loss in air and nitrogen at 445–515 and 500–520°C, respectively. The crosslinking reaction of some benzylidenependant polyphthalimidines took place at 300°C through double‐bond addition to afford cured polymers with improved thermal stability.