Abstract: A series of flame retardant thermotropic wholly aromatic copolyesters were derived from acetylated 2-(6-oxido-6H-dibenz<c,e><1,2>oxa phosphorin-6-yl)-1,4-dihydroxy phenylene(DOPO-HQ), p-acetoxybenzoic acid(p-AHB), terephthalic acid(TPA) and isophthalic acid(IPA) by melting polycondensation. The structure and basic properties of polymers, such as glass transition temperature(T_g), melting temperature(T_m), thermal stability, and liquid crystallinity were investigated by FTIR, elemental analysis, differential scanning calorimetry(DSC), thermogravimetry analysis(TGA), and thermal polarized optical microscope. The copolyesters have relative high T_g values which range from 456 to 465 K. The T_m obtained from DSCcurves(P-20 and P-25) and initial flow temperatures(T_f) observed on hotstage polarizing microscope are from 544 to 568 K. The decomposing temperatures(T_d50%) in nitrogen range from 704 to 735 K, and char yields at 923 Kare 41～52. All the copolyesters, except P-40, are thermotopic and nematic.

Key words: Thermotropic copolyesters, Thermal behaviour, Flame retardancy