Synthesis and liquid crystalline properties of new thermotropic polyurethanes

Mesogenic diol monomer, terephthaloyl dioxydibenzoic acid diol eater (n = 2 , 3, 4, 5, 6), were prepared from omega-hydroxyalkyl-4-hydroxybenzoate and terephthalyl chloride, using Schotten-Baumann Reaction. New liquid crystall ine polyurethanes (LCPUs) were obtained by solution polymerization mesogeni c diol monomers with 4,4'-diphenylmethane diisocyanate (MDI) and 2,4-tolyle ne diisocyanate (2,4-TDI). The monomer and polyurethanes were investigated by DSC, polarizing microscopy, wide-angle X-ray diffraction (WAXD), small-a ngle X-ray diffraction (SAXD) and high temperature X-ray diffraction. All L CPUs synthesized showed a nematic LC nature with wide temperature range.