MACROCYCLIC ARAMIDS (2N-AZA[2N]PARACYCLOPHANE-2N-ONES) - NEW INTERMEDIATES FOR THE SYNTHESIS OF P-ARAMIDS

An easy route to a new class of 2n-aza[2n]paracyclophane-2n-ones, N-substituted para-oriented cyclic aromatic amide (cycloaramid) oligomers, is described. The bulky diamine N,N'-di-sec-butyl-p-phenylenediamine is condensed with terephthaloyl chloride at elevated temperature in o-dichlorobenzene to provide a high yield of N,N'-di-sec-butyl-p-phenyleneterephthalamide cyclic oligomers (from dimer to tridecamer). (There is evidence presented for the presence of cyclic unimer (a single repeat unit), an amide analog of [2.2]paracyclophane, in the reaction product!) The cyclization is favored by the cis conformation of the N-substituted amide bonds present in the growing chain. Ring-opening polymerization of these new cycloaramids to high molecular weight linear polymers can be effected in the melt phase with highly nucleophilic catalysts such as 1,3-dialkylimidazole-2-thiones, especially when an acid cocatalyst is employed. The N-substituted polymers yield crystalline films and fibers with an axial repeat length which can only be explained by an unexpected trans conformation of the amide bonds. The facile synthesis of other macrocyclic amides by the steric control of macrocyclization by N-substitution of the amide bond is also described.