Synthesis and characterization of main chain liquid crystalline ionomers containing sulphonate groups

A series of main chain liquid crystalline ionomers containing sulphonate groups pendent to the polymer backbone were synthesized by an interfacial condensation reaction of 4,4'-bis(1,10-sebacyloxo)benzoic acid, brilliant yellow (BY), and 4,4'-biphenyldiol. 4,4'-Bis(1,10-sebacyloxo)benzoic acid exhibited nematic schlieren texture during heating and cooling. The ionomers are thermotropic liquid crystalline polymers and thermally stable to about 270°C. They exhibit broad mesophase regions over a range of 220°C and the same nematic mesomogen with a colourful thread texture as B₀-LCP, which implies that the introduction of an ionic group did not change the texture of the B₀-LCP. However, the thermotropic liquid crystalline properties were somewhat weakened when the concentration of BY was more than 5%. The inherent viscosity in N,N-dimethylformamide solution suggested that intermolecular associations of sulphonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration.