PREPARATION AND THERMOTROPIC LIQUID-CRYSTALLINE PROPERTIES OF SEMIRIGID COPOLYURETHANES COMPOSED OF BIPHENYL UNITS AND PARTIALLY FLUORINATED ALIPHATIC CHAINS

New semirigid thermotropic liquid crystalline (LC) copolyurethanes 4 a nd 5 made up of biphenyl units and partially fluorinated aliphatic cha ins in the backbones were synthesized by melt polycondensation of a mi xture of a dioxydihexanol of biphenyl 1 and two fluorine-containing di ols 2a,b taken in definite feed mole ratios with alkylene diphenyl dic arbamates 3a-i having various lengths of aliphatic chains. The assigne d structures of copolyurethanes 4 and 5 were identified by FTIR, H-1- and C-13-NMR spectra, and elemental analyses. The thermal and mesogeni c properties were evaluated by differential scanning calorimetry (DSC) , thermal mechanical analyses (TMA), polarizing microscopy, and temper ature-changeable X-ray analyses, whose measurements indicated that the copolymers 4 and 5 form thermotropic nematic phases and have glass tr ansition steps around room temperature. It is suggested that the incor poration of partially fluorinated aliphatic chains into the backbones has no drastic effect on the LC formation in the semirigid copolyureth anes 4 and 5. (C) 1998 John Wiley & Sons, Inc.