A Novel Thermotropic Liquid Crystalline Copolyester Containing Phosphorus and Aromatic Ether Moity Toward High Flame Retardancy and Low Mesophase Temperature

A series of thermotropic liquid crystalline polyesters containing phosphorus and aromatic ether groups (TLCP-AEs) were synthesized from p-acetoxybenzoic acid (p-ABA), terephthalic acid (TPA), 4,4'-oxybis(benzoic acid) (OBBA), and acetylated 2-(6-oxid-6H-dibenz(c,e) (1,2) oxaphosphorin 6-yl) 1,4-benzenediol (DOPO-AHQ). The chemical structure and the properties of TLCP-AEs were characterized by Fourier-transform spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (H-1 NMR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electronic microscopy (SEM), polarizing optical microscopy (POM), limiting oxygen index, and UL-94 tests, respectively, The results showed that TLCP-AEs had low and broad mesophase temperatures (230-400 degrees C). TLCP-AEs also showed excellent thermal stability; their 5%-weight-loss temperatures were above 440 degrees C and the char yields at 700 degrees C were higher than 45 wt %. All TLCP-AE polyesters exhibited high flame retardancy with a LOI value of higher than 70 and UL-94 V-0 rating. The SEM observation revealed that TLCP-AEs had good fibrillation ability. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1182-1189, 2010