A novel phosphorus-containing thermotropic liquid crystalline poly(ester-imide) with high flame retardancy

A novel phosphorus-nitrogen thermotropic liquid crystalline poly(ester-imide)(PN-TLCP) derived from p-acetoxybenzoic acid (ABA), terephthalic acid (TPA), acetylated 2-(6-oxide-6H-dibenz < c,e >< 1,2 > oxa phosphorin-6-yl)-1,4-dihydroxy phenylene (DOPO-AHQ) and N,N'-hexane-1,6-diylbis(trimellitimide) was prepared by melt trans-esterification. The chemical structure, the mesophase behavior, and the thermal properties of the copolymer were investigated with Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy [H-1 NMR), elemental analysis, wide-angle X-ray diffraction (WAXD), hot-stage polarized light microscopy (PLM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). PN-TLCP exhibited a nematic mesophase with a strong birefringence at a low and broad mesomorphic temperature ranging from 220 to 350 degrees C, an initial flow temperature as low as about 190 degrees C and a glass transition temperature of about 160 degrees C. PN-TLCP has also good thermal stability, high char residues and excellent flame retardancy (limiting oxygen index, LOI = 71 and UL-94 V-0 rating). Copyright (C) 2009 John Wiley & Sons, Ltd.