| Abstract: | A new aromatic polyamide containing a pendant ethoxycarbonyl group was successfully synthesized from the reaction between 4,4′‐diamino‐2′‐ethoxycarbonylbenzanilide and terephthaloyl chloride. The new polymer was soluble in organic solvents such as N‐methyl‐2‐pyrrolidone and dimethylacetamide, and a tough and transparent film was cast from the polymer solution with viscosities ranging from 2.6 to 5.6 dL/g. When the polymer film was heat‐treated at a temperature greater than 300 °C, a cyclization reaction occurred between the ethoxycarbonyl group and the adjacent amide bond to form a benzoxazinone unit in the polymer backbone. The thermal decomposition onset temperature of the cyclized film was about 523 °C, which was somewhat lower than that of poly(p‐phenylene terephthalamide) (PPTA; 566 °C); however, the decomposition rate was slower than that of PPTA to yield a higher char residue. The dispersion temperature of the uncyclized poly(4,4′‐diamino‐2′‐ethoxycarbonylbenzanilide terephthalamide) (PDEBTA) was about 340 °C, whereas that of the cyclized PDEBTA was not clear. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 936–942, 2000 |
