Polyimides Containing a Quinazolinone Moiety

A novel heterocyclic diamine monomer, 2-(4-aminophenyl)-6-amino-4(3 H )-quinazolinone was synthesized from readily available compounds in three steps in high yield. A series of novel polyimides containing the quinazolinone moiety were synthesized either by a one-step solution polymerization reaction or by a two-step procedure that included a ring-opening polyadddition to give poly(amic acid)s, followed by cyclodehydration to polyimides. In the one-step method in m -cresol or p -chlorophenol with isoquinoline catalyst, polyimides with inherent viscosities of 0.44−0.63 dL/g were obtained. Polyimides 4f and 4g from dianhydrides which have a flexible linkage, hexafluoroisopropylidene dianhydride ( 2f ) and BPA dianhydride ( 2g ), were soluble in hot m -cresol and could be cast into tough films from m -cresol solution. In the two-step method, poly(amic acid)s with inherent viscosity between 0.63 and 1.40 dL/g were obtained in DMAc at room temperature. The poly(amic acid)s were converted to the corresponding polyimide films by thermal cyclodehydration. The T g values of the polyimides ranged from 298 to 350 °C. Polyimide 4a from pyromellitic dianhydride ( 2a ) did not show a clear transition in the DSC. Polyimides 4b from biphenyltetracarboxylic dianhydride ( 2b ) and 4g were semicrystalline and showed clear endothermic peaks for T m at 465 and 356 °C, respectively. Degradation temperatures for 5% weight loss all occurred above 540 °C in nitrogen and above 537 °C in air. Young's moduli of thin films ranged from 2.34 to 4.89 GPa at room temperature and they maintained the high moduli to high temperatures. The monomer was successufuly copolymerized with 4,4‘-oxydianiline and 2g . With increasing incorporation of quinazolinone units, the copolymers had higher T g values, were more thermally stable, and had higher moduli.