Aliphatic–aromatic copolyesters containing phosphorous cyclic bulky groups

A series of phosphorus-containing copolyesters was prepared by polycondensation of 2-(6-oxido-6H-dibenz<c,e><1,2>oxaphosphorin-6-yl)-1,4-naphthalene diol, 1, or of an equimolecular amount of 1 and different aliphatic diols 2, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and 1,12-dodecanediol, 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 decomposition temperature above 375 °C. The glass transition temperature was in the range of 96–146 °C. The polymers exhibited thermotropic liquid crystalline behavior, as was observed with polarized optical microscopy. DSC and X-ray experiments were also found in concordance with mesophase formation.