Synthesis and liquid crystalline properties of new thermotropic polyurethanes

Mesogenic diol monomer, terephthaloyl dioxydibenzoic acid diol ester (n = 2, 3, 4, 5, 6), were prepared from ω-hydroxyalkyl-4-hydroxybenzoate and terephthalyl chloride, using Schotten-Baumann Reaction. New liquid crystalline polyurethanes (LCPUs) were obtained by solution polymerization mesogenic diol monomers with 4,4 prime -diphenylmethane diisocyanate (MDI) and 2,4-tolylene diisocyanate (2,4-TDI). The monomer and polyurethanes were investigated by DSC, polarizing microscopy, wide-angle X-ray diffraction (WAXD), small-angle X-ray diffraction (SAXD) and high temperature X-ray diffraction. All LCPUs synthesized showed a nematic LC nature with wide temperature range.