Synthesis and Properties of Novel Main-Chain Liquid Crystalline Polyurethanes Prepared from 4, 4′-Bis (ω-hydroxyalkyleneoxy) biphenyls and Methyl (S) -2, 6-diisocyanatohexanoate

Novel thermotropic liquid crystalline polyurethanes were prepared from 4, 4′-bis (ω-hydroxyalkyleneoxy) biphenyl (BHBm) and methyl (S) -2, 6-diisocy-anatohexanoate (LDI). The intrinsic viscosities of the polymer were in the range 0.52-0.79dL/g. Structural characterization was carried out by elemental analysis, FT-IR spectroscopy and nuclear magnetic resonance (1H NMR) spectroscopy. Optical and thermal methods reveal that this polyurethane exhibits monotropic mesomorphic behavior. Differential scanning calorimetry (DSC) shows a crystalline melting transition that is highly dependent on the molecular weight, the flexible spacer length and the diisocyanate. The thermalstability was determined by thermogravimetric (TG) analysis.