| Abstract: | Thermotropic main chain liquid crystalline polyurethanes were prepared from 4-{4-(6-hydroxyhexyloxy)phenylimino]methyl}benzoic acid 4-{4-(6-hydroxyhexyloxy)phenylimino]methyl}phenyl ester (mesogenic diol) and 1,6-hexamethylene di-isocyanate. The effects of partial replacement of the mesogenic diol by 20-50 mol% of poly(tetramethylene oxide)glycol (PTMG) of varying molecular mass (M n =650, 1000, 2000) on the liquid crystalline properties were studied. Structural characterization was carried out by FTIR spectroscopy and the molecular mass distribution was determined by GPC. Differential scanning calorimetry and hot stage polarizing optical microscopy were used to study the mesomorphic properties. It was observed that the partial replacement of the mesogenic diol by PTMG of varying molecular masses influenced the phase transitions and the occurrence of mesophase textures. When the molecular mass of PTMG was enhanced, a higher content of mesogenic agent was needed to obtain liquid crystalline properties. |
