A novel phosphorus-containing thermotropic liquid crystalline copolyester with flexible spacers (P-TLCP-FS) was synthesized by melt transesterification from p-acetoxybenzoic acid (p-ABA), terephthalic acid (TPA), ethylene glycol, and acetylated 2-(6-oxid-6H-dibenz(c,e) (1,2) oxaphosphorin 6-yl) 1,4-benzenediol (AODOPB). The chemical structure and properties of the obtained P-TLCP-FS were characterized by Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (H-1-NMR), inherent viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TGA), polarizing light microscopy (PLM), and X-ray diffraction (XRD) analysis. P-TLCP-FS had inherent viscosities of 0.92-1.12 dL/g and exhibited low and wide mesophase temperatures, ranging from 185 to 330 degrees C, which can match with the processing temperatures of most conventional polymers and high flame retardancy with a limiting oxygen index value of 70% and UL-94 V-0 rating. (c) 2008 Wiley Periodicals, Inc.