Liquid–crystalline copoly(ester–amide)s prepared from hydroxybenzoic and 4‐aminobenzoic acids

Copolycondensations of 3,5‐dimethoxy‐4‐hydroxybenzoic (syringic acid, SGA), 4‐hydroxybenzoic(PHB), and 4‐aminobenzoic (PAB) acids with diphenyl chlorophosphate(DPCP)/LiCl/pyridine were studied. Random copolycondensations of a wide range of monomer compositions afforded copolymers exhibiting birefringence at room temperature. However, when the sequence of PHB and PAB was fixed by using a newly prepared monomer, 4‐(4′‐aminobenzoyloxy) benzoic acid (PABBA), the ordered copolymers thus prepared showed birefringence above 200°C, but not at room temperature. Variations in solubility and thermal behavior were also observed in randomly and sequentially prepared copolymers. The monomer sequences in copolymers in random copolycondensations could be changed by controlling the reaction of monomers with DPCP.