POLYMERS BASED ON PARAAMINOPHENOL .6. FACILE SYNTHESIS OF THE SIMPLEST WHOLLY AROMATIC POLY(IMIDE ESTER) BY PYROLYTIC POLYMERIZATION OF MONOMERS CONTAINING PREFORMED ESTER LINKAGES

An improved synthetic procedure for a wholly aromatic poly(imide-ester) with the simplest structure has been examined. The polymer was synthesized through imide formation polymerization by pyrolytic condensation of monomers containing preformed ester linkages and evaluated as a high performance polymer. The monomers were prepared by first N-protection of p-aminophenol with phenyl chloroformates followed by acylation of the remaining hydroxyl group with trimellitic anhydride acid chloride. Thermal analysis revealed that these monomers underwent pyrolysis to split off the corresponding phenols and carbon dioxide giving rise to the poly(imide-ester). Pyrolysis behavior was closely associated with the substituents on the phenol moiety; the monomers having electron-withdrawing groups showed improved thermal dissociation and hence resulted in the formation of poly(imide-esters) with higher viscosities. This procedure was much superior to the previous one involving the ester-forming polymerization. The resulting poly(imide-esters) had inherent viscosities up to 0.38 dL/g in concentrated sulfuric acid. Thermogravi-metric analysis showed high thermal stability with a weight loss of only 2% at 500 °C with a heating rate of 5 °C/min in air. © 1990, American Chemical Society. All rights reserved.