Synthesis and mesogenic properties of polyurethanes containing a naphthalene ring

New polyurethanes with high inherent viscosities of 1.74-2.10 dl/g in 1,1,1,3,3,3-hexafluoro-2-propanol were prepared by melt polycondensation of a 2,6-dioxydihexanol derivative of naphthalene, prepared from naphthalene-2,6-diol and 6-chloro-1-hexanol, with even alkylene diphenyl dicarbamates (n = 6, 8, 10 and 12). The structures of the polymers were confirmed by FTIR, 13C-NMR spectra and elemental analyses. Thermotropic liquid-crystalline (LC) properties of the polyurethanes were evaluated by differential scanning calormetry, by optical texture observation with a polarizing microscope and with an X-ray diffractometer. It was discovered that polyurethanes having only the naphthalene ring could form nematic LC textures in spite of the low aspect ratio of the mesogenic unit.