Synthesis, characterization, and thermal properties of phosphorus-containing, wholly aromatic thermotropic copolyesters

Abstract

A series of phosphorus-containing, wholly aromatic thermotropic copolyesters from acetylated 2-(6-oxide-6H-dibenz〈c,e〉〈1,2〉 oxa phosphorin-6-yl)-1,4-dihydroxy phenylene, p-acetoxybenzoic acid, terephthalic acid, and isophthalic acid were prepared by melting polycondensation. The structure and basic properties of the polymers, such as the glass-transition temperature (Tg), melting temperature (Tm), thermal stability, crystallinity, and liquid crystallinity, were investigated with Fourier transform infrared, elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis, wide-angle X-ray diffraction, and hot-stage polarizing optical microscopy. The copolyesters had relatively high Tg values ranging from 183 to 192°C. The Tm values obtained from DSC curves for samples P-20 and P-25 were 290 and 287°C, respectively (where the number in the sample name indicates the molar fraction of the phosphorus-containing monomer in the reactants). The initial flow temperatures of other samples observed with hot-stage polarizing microscopy were 271-290°C. The 5% degradation temperatures in nitrogen ranged from 431 to 462°C, and the char yields at 640°C were 41-52%. All the copolyesters, except P-40, were thermotropic and nematic. © 2002 Wiley Periodicals, Inc. J. Appl. Polym. Sci.