Liquid–crystal azopolyamides with high thermal stability and inherent viscosity

In order to get novel photochromic fiber-forming polyamides with liquid crystal (LC), high inherent viscosity and thermal stability properties, two linear azobenzene polyaramides were synthesized by alternative polycondensation reactions of trans-azobenzene-4,4′-dicarbonyl chloride with various diamine monomers without any substituents under low temperature. As expected, the resulting polyamides exhibit high degree of crystallinity (the highest value reaches 52%), inherent viscosity (the highest value reaches 4.26 dL/g), and thermal stability (≤5% weight loss at 350 °C) due to intensively intermolecular hydrogen bonding and extremely symmetric and rigid molecular structures, which were identified by FT-IR spectroscopy and elemental analysis. Moreover, important liquid crystal and photoisomerization properties for optical devices and photochromics fibers spinning are also observed in N,N-dimethylacetamide (DMAc) solutions due to the regular rigid structure and intermolecular hydrogen bonding. The synthesized azo polyamides are suitable for fiber spinning and can be applied in fields of potential optical techniques and novel anti-ultraviolet and photochromic fibers industry at wide temperature ranges.