Liquid Crystalline Ionomers: 2. Synthesis and Characterization of a Main-Chain Liquid Crystalline Polymer Containing Terminal Sulfonate Groups
Liquid crystalline ionomers containing sulfonate groups on the terminal unit of the chain were synthesized by an interfacial condensation reaction of 4,4′-dihydroxy-α,α′-dimethyl benzalazine, the monofunctional dye fast yellow (FY), and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. The weight-average molecular weights were estimated from inherent viscosity measurements to be between 6000–11,000 and the sodium sulfonate concentrations ranged from 0–18.4 meq/100 g polymer. Elemental analyses, however, indicated much higher molecular weights, which suggested that there was a distribution of chains with one, two, or no FY endgroups. The polymers were semicrystalline and melted at ca. 140°C to form nematic mesophases that were stable over a temperature range of ca. 80°C. They were thermally stable to about 350°C. The ionomeric nature of the polymers was confirmed by the presence of intermolecular associations in nonpolar solvents, as demonstrated by dilute solution viscosity measurements.