S. N. Jaisankar, University of Oklahoma, Department of Chemistry, Norman, OK 73072, Y. Lakshminarayana, Central Leather Research Institute, Polymer Division, Adyar, Chennai, 600 020, India, Christopher Brammer, Cbme, University of Oklahoma, 100 E. Boyd St., T-335, Norman, OK 73019, and Donna J. Nelson, Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, OK 73019.
Reacting the ionic chain extender DBS with an isocyanate prepolymer unexpectedly produced liquid crystal polyurethane-ureas (PUUs), which each display characteristics of a distinct monotropic nematic phase upon slow cooling, which is a rare mesophase in ionic liquid crystals. Phase transition temperatures and morphology of these thermotropic liquid crystal PUUs were determined by hot-stage optical polarizing microscopy, FTIR, CP/MAS 13C NMR, VPO, DSC, and TG/DTA. The proposed liquid crystal phase and the influence of the ionomer structure in each PUU are discussed in detail. The PUU texture is dependent upon the PUU isocyanate; HDI and IPDI polymers have nematic schlieren textures, whereas TDI and MDI polymers show nematic grain textures.