Novel thermal stable organosoluble polyamides and polyimides based on quinoxalin bulky pendent group

Abstract

A new diamine containing a bulky diphenylquinoxalin pendant, 3,5-diamino-N-(2,3-diphenylquinoxalin-7-yl)benzamide (DQB), was synthesized in four steps through the nucleophilic aromatic substitution of 3,5-dinitrobenzoylchloride with 2,3-diphenylquinoxalin-6-amine and subsequent catalytic reduction. All intermediates and DQB were fully characterized by FTIR, NMR and elemental analysis. A series of polyamides PA(a–e) was synthesized from this diamine by direct polycondensation with various dicarboxylic acids, triphenyl phosphate and pyridine in N-methyl-2-pyrrolidynone (NMP). Three polyimides PI(a–c) were synthesized from this diamine using commercial dianhydrides in two-step polycondensation. Characterization of polymers was accomplished by FTIR, H NMR, elemental analysis, DSC, DMTA, GPC, and TGA. The intrinsic viscosities of PAs ranged from 0.54 to 0.67 dL/g. PAs displayed T g values of 140–298 °C and 10% weight loss of 415–485 °C in N2. The T g values of the PIs varied between 200 and 310 °C, with 10% weight loss above 500 °C in N2. The PAs were soluble in common polar aprotic solvents at room temperature whereas the aromatic PIs were dissolved by heating at 60 °C.