QUANTUM SEMIEMPIRICAL STUDIES ON THE FORMATION OF AROMATIC POLYAMIDES.1. EFFECT OF STRUCTURAL PARAMETERS OF DIAMINES ON THE POLYAMIDATION REACTION

A semiempirical quantum-mechanical study of structural and electronic parameters of aromatic diamines was performed using the method AM1. Th e diamines have been considered as condensation monomers, and the reac tivities of both amino groups against acyl chlorides have been compute d. The study shows that the amidation reaction is controlled mainly by the global charge on the amino group and, in a much smaller extent, b y the frontier orbitals. This behaviour is consistent with the large e nergy gap between the HOMO(a)) of the diamine and the LUMO(b)) of the acyl chloride. It has been found also that the electronic nature of th e substituents, affecting the charge of the amino groups, greatly affe cts the carbons directly joined to these groups. This permits to corre late the reactivities with the calculated charges on these carbons.