Preparation and properties of a new aromatic polyamide with an ethoxycarbonyl pendant group: Poly(4,4 '-diamino-2 '-ethoxycarbonyl-benzanilide terephthalamide)

A new aromatic polyamide containing a pendant ethoxycarbonyl group was succ essfully synthesized from the reaction between 4,4'-diamino-2'-ethoxycarbon ylbenzanilide and terephthaloyl chloride. The new polymer was soluble in or ganic solvents such as N-methyl-2-pyrrolidone and dimethylacetamide, and a tough and transparent film was cast from the polymer solution with viscosit ies ranging from 2.6 to 5.6 dL/g. When the polymer film was heat-treated at a temperature greater than 300 degrees C, a cyclization reaction occurred between the ethoxycarbonyl group and the adjacent amide bond to form a benz oxazinone unit in the polymer backbone. The thermal decomposition onset tem perature of the cyclized film was about 523 degrees C, which was somewhat l ower than that of poly(p-phenylene terephthalamide) (PPTA; 566 degrees C); however, the decomposition rate was slower than that of PPTA to yield a hig her char residue. The dispersion temperature of the uncyclized poly(4,4'-di amino-2'-ethoxycarbonylbenzanilide terephthalamide) (PDEBTA) was about 340 degrees C, whereas that of the cyclized PDEBTA was not clear. (C) 2000 John Wiley & Sons, Inc.