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) macromonomers were prepared and subjected to the preparation of tailor-made aromatic thermotropic liquid-crystalline (LC) polyester-graft-PPO copolymers. The macromonomers were obtained by hydrolysis of dimethyl carboxylate-terminated PPO macromonomers without cleavage of the PPO chains, which were derived from PPO oligomers with a terminal phenolic OH-group and a bromo derivative of isophthalate. The tailor-made aromatic thermotropic LC graft copolymers were prepared by direct polycondensation from the dicarboxy-terminated macromonomers, p-hydroxybenzoic acid, aromatic dicarboxylic acids and diphenols at definite mole ratios in pyridine in the presence of diphenyl chlorophosphate as a condensation reagent. The polyester-graft-PPO copolymers are thermally stable up to 280–300°C and show a thermotropic LC nematic phase in spite of introduction of PPO grafts on the polyester backbones.