THERMOTROPIC LIQUID-CRYSTALLINE AROMATIC POLYESTER-GRAFT-POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) COPOLYMERS

Dicarboxy-terminated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) macr omonomers were prepared and subjected to the preparation of tailor-mad e aromatic thermotropic liquid-crystalline (LC) polyester-graft-PPO co polymers. The macromonomers were obtained by hydrolysis of dimethyl ca rboxylate-terminated PPO macromonomers without cleavage of the PPO cha ins, which were derived from PPO oligomers with a terminal phenolic OH -group and a bromo derivative of isophthalate. The tailor-made aromati c thermotropic LC graft copolymers were prepared by direct polycondens ation from the dicarboxy-terminated macromonomers, p-hydroxybenzoic ac id, aromatic dicarboxylic acids and diphenols at definite mole ratios in pyridine in the presence of diphenyl chlorophosphate as a condensat ion reagent. The polyester-graft-PPO copolymers are thermally stable u p to 280-300 degrees C and show a thermotropic LC nematic phase in spi te of introduction of PPO grafts on the polyester backbones.