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Abstract
Novel polyurethanes have been synthesized by the condensation of two rigid diols, biphenyl-4,4′-diol (BPH(4,4′)D) and 4-hydroxyphenyl-4-hydroxybenzoate (4HPH4′HB), with the flexible hexamethylene diisocyanate (HDI). Their phase diagrams were established by means of differential scanning calorimetry, nuclear magnetic resonance and polarizing optical microscopy. Poly(4HPH4′HB/HDI) was found to display a nematic phase between 140 and 199°C; poly (BPH(4,4′)D/HDI) also exhibits a mesomorphic phase, but so far the nature of this phase has not been established.