Synthesis and characterization of aromatic polyamides based on a bis(ether-carboxylic acid) or a dietheramine derived from tert-butylhydroquinone

Abstract

1,4-Bis(4-carboxyphenoxy)-2-tert-butylbenzene (2a) and 1,4-bis(4-aminophenoxy)-2-tert-butylbenzene (2b) were synthesized in two steps starting from the nucleophilic aromatic substitution reaction of p-fluorobenzonitrile and p-chloronitrobenzene, respectively, with tert-butylhydroquinone in the presence of potassium carbonate in N,N-dimethylformamide (DMF). Aromatic polyamides were synthesized by direct polycondensation from diacid 2a with various diamines or from diamine 2b with various diacids, by means of triphenyl phosphite and pyridine in N-methyl-2-pyrrolidone solution containing calcium chloride. Inherent viscosities of the polyamides ranged from 0.64 to 1.04 dL/g. Almost all the polyamides are readily soluble in various organic solvents and afford transparent and tough films by solvent casting. The polyamides display T g values of 209-267°C and 10% weight loss values above 460°C in nitrogen and 439°C in air. A comparative study of some polyamides with an isomeric repeating unit is also presented.