A series of poly(ester imide ketone)s (PEIKs) with varied p-hydroxybenzoic acid (HBA) molar fraction derived from N,N'-hexane-1,6-diylbis(trimellitimide), 4,4'-dihydroxybenzophenone, and p-hydroxybenzoic acid were synthesized by a "step-feeding" polycondensation method in benzene sulfonyl chloride, dimethylformamide, and pyridine. High field H-1, C-13, and 2D NMR spectroscopy measurements were combined to determine the assignments of hydrogen and carbon atoms in the copolymers. C-13 inverse gated decoupling NMR spectra were taken and used as a quantitative method to analyze the chain sequence structures of these copolymers. The liquid crystalline behaviors and thermal properties of the PEIKs were characterized by polarized light microscopy (PLM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The NMR studies show that the monomeric unit ratios of the PFIKs are very close to the ratios of the monomers added into the polycondensation process. The analytical results of sequence distribution indicate that the sequence ratios of I-H, H-D, and H-H dias rise with the increase of HBA molar fraction, while that of I-D decrease. It is worth noting that the sequence ratios of H-H are always very small among the four sequence ratios although the HBA molar fraction varied from 0 to 50%. It was shown that the copolymers possess a typical nematic thermotropic liquid crystalline character and high thermal stability, which is strongly related with the changes in sequence structure of the molecular chains. This type of liquid crystalline polymers also exhibits excellent fiber-forming character in the melting state, which would find its potential usages in high performance fiber and fiber modification materials. (c) 2006 Wiley Periodicals, Inc.