Unexpected Discovery of the Formation of High-Molecular-Weight Aromatic Polyamides from Unstoichiometric Diacyl Chloride/Diamine Components

Two bis(ether-benzoylchloride)s, 4,4′-(1,4-phenylenedioxy)dibenzoylchloride (I) and 4,4′-(1,4-naphthalenedioxy)dibenzoyl chloride (II), were unexpectedly synthesized through nucleophilic substitution reaction of p-fluorobenzonitrile with 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-benzenediol (1) and 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-naphthalenediol (2), respectively, followed by hydrolysis and chlorination. A series of aromatic poly(ether-amide)s, having inherent viscosities of 0.65–0.99 dl g −1 , prepared by the low-temperature solution polycondensation from the diacid chloride I with various aromatic diamines in an initial feeding molar ratio of diamine:diacyl chloride of 1:1 and 1:1.55, respectively. All resultant poly(ether-amide)s showed high and similar inherent viscosity regardless of the great stoichiometric imbalance. The unexpected results could be attributed to the very slow dissolution rate of the diacid chloride I in the reaction solvents such as N-methyl-2-pyrrolidone and N,N-dimethylacetamide.