New synthesis and characterization of ionic polyurethane-urea liquid crystals

A new series of thermotropic ionic polyurethane-urea (PUU) liquid crystals (LCs) were synthesized, each by using the corresponding diisocyanate, 4,4′-bis(6-hydroxyhexoxy)biphenyl, and sodium 2,5-diaminobenzenesulfonate. Morphology, phase transition temperatures, and spectroscopic characteristics of the PUU LCs are reported. Each PUU exhibits a monotropic liquid crystal phase upon slow cooling. The PUU LC phase texture is visible by polarized optical microscopy (POM) and is dependent upon the PUU isocyanate precursor; 1,6-diisocyanatohexane (HDI) and 5-isocyanato-1-(isocyanatomethyl)-1,3,3,-trimethylcyclohexane (IPDI) polymers have schlieren textures, whereas 2,4-diisocyanato-1-methylbenzene (TDI) and methylenebis(4-phenylisocyanate) (MDI) polymers show grain textures.