Studies on thermotropic liquid crystalline polymers. XVI. Synthesis and properties of fully aromatic poly(amide-ester)s with naphthalene structures

Abstract

A series of novel, fully aromatic high-molecular-weight poly(amide-ester)s was prepared by the direct polycondensation from terephthalic acid (TPA) and 2,6-naphthalene dicarboxlic acid (NDC) with various aromatic diols and diamines in the presence of diphenyl chlorophosphate (DPCP), LiCl, and pyridine. The structures and thermal properties of these synthesized poly(amide-ester)s were examined by FTIR, wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal polarized optical microscope, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of the kinds of the aromatic diols and diamines (bisphenyl units, naphthalene, and (un)substituted phenylene structures) on the thermal properties of the synthesized poly(amide-ester)s were investigated in this study. Strong interchain interactions were induced by using a 50 : 50 molar ratio of the amide groups to the ester groups, and, thus, no LC properties but good thermal stabilities were found in all of the synthesized poly(amideester)s containing naphthalene, substituted hydroquinone, or bisphenol segments in this study. However, another series of poly(amide-ester)s with a molar ratio of diamine to diol of 20 : 80 exhibited excellent mesophase stabilities, with various molar ratio of terephthalic acid (TPA) to 2,6-naphthalene dicarboxlic acid (NDC).