Naphthalene-based crystalline polyamides and polyesters

Abstract

Two families of aromatic-aliphatic poly(alkylene-1,5-naphthaleneamide)s and poly(alkylene-1,5-naphthanoate)s were prepared by means of single phase solution polymerizations. After workup and drying, the polymers exhibited very high degrees of crystallinity. Wide-angle X-ray diffraction patterns of the polymers revealed a significant similarity in the crystal structure of the polyamides and polyesters. In both of them, the naphthalene condensed rings were preferentially stacked upon one another and when the alkylene segments were sufficiently long, they were not fully extended. Infrared spectroscopy indicated that in the case of the polyamides, all the amide groups were hydrogen bonded to each other. This fact exhibited itself by the glass transition temperatures of the polyamides being higher than those of the corresponding polyesters and, especially, in the melting points of the polyamide crystals being much higher than those of the polyester analogues. Most of the polymers prepared in this work were of molecular weights too low for developing good mechanical properties, and their window for melt processing too narrow for comfort.