Synthesis and properties of new aromatic copolyesters containing phosphorous cyclic bulky groups

A series of phosphorus‐containing copolyesters was prepared by polycondensation of 2‐(6‐oxido‐6H‐dibenz<1,2>oxaphosphorin‐6‐yl)‐1,4‐naphthalene diol, 1 , or of an equimolecular amount of 1 and different bisphenols 2 , such as 4,4′‐isopropylidenediphenol, 4,4′‐(hexafluoroisopropylidene)diphenol and 2,7‐dihydroxynaphthalene, with an aromatic diacid chloride containing two preformed ester groups 3 , namely, terephthaloyl‐bis‐(4‐oxybenzoyl‐chloride). The copolyesters exhibited good thermal stability having the temperature of 5% weight loss above 380°C and char yield at 700°C in the range of 20–31.2%. The glass transition temperature was in the range of 136–147°C. The polymers exhibited thermotropic liquid crystalline behavior, as was observed with polarized optical microscopy, differential scanning calorimetry, and X‐ray experiments. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers