Molecular design and synthesis of thermotropic liquid crystalline poly(amide imide)s with high thermal stability and solubility

A series of thermotropic liquid crystalline poly(amide imide) s (PAIs) with well-defined structure were prepared by the Yamazaki-Higashi phosphorylation method. To obtain the target polymers, several diimide diacid monomers (DIDAs) as mesogenic units were synthesized by the dehydration cyclization of aromatic anhydride with aliphatic 11-aminoundecanoic acid (AU). The chemical structure of these DIDAs and PAIs was confirmed via Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (H-1-NMR) spectroscopy. Thermotropic liquid crystalline characteristics of the DIDAs and PAIs were investigated by differential scanning calorimetry (DSC), polarizing light microscopy (PLM) and X-ray diffraction (XRD) analysis. Encouragingly, all of these liquid crystalline PAIs exhibited good thermal stability, in which the decomposition temperatures are much higher than the melting temperatures of PAIs. Furthermore, the liquid crystalline PAIs can be dissolved into some common solvents such as dimethyl sulfoxide (DMSO) and m-cresol, which indicates these liquid crystalline PAIs could be processed not only by melting-processing but also by solution spin-coating.