SYNOPSISThe thermal degradation mechanisms of liquid crystalline aromatic polyesters ( LCPs ) prepared from p -hydroxybenzoic acid ( P H B ) , biphenol ( B P ) , and terephthalic acid (TA)were studied by pyrolysis-gas chromatography/mass spectrometry ( Py-GC/MS) . The LCP containing deuterated terephthalate units and the LCPs that have different comonomer ratios were examined. On the basis of the pyrolysis products determined, the origin of the main pyrolysis products (benzene, phenol, biphenyl, phenyl benzoate, etc.) from the corresponding comonomer units were estimated and their thermal degradation mechanisms were eventually discussed in detail.

Compositional analyses of liquid crystalline aromatic polyesters prepared from p-hydroxybenzoic acid (PHB), terephthalic acid (TA) and biphenol (BP) were examined using NMR, IR, pyrolysis-GC and hydrolysis-HPLC. The best method was hydrolysis-HPLC. Hydrolysis of the polymers was carried out under the condition of strong alkalinity and high temperature; the obtained monomers were determined by HPLC. Small amounts of other comonomers and impurities could be determined at the same time. This method is also applicable to the compositional analysis of other systems of liquid crystalline polyesters.

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