As. Angeloni et al., SYNTHESIS AND LIQUID-CRYSTALLINE PROPERTIES OF THERMOTROPIC POLY(ESTER-URETHANE)S, European Polymer Journal, 31(3), 1995, pp. 253-258
Seven new mesogenic diol monomers CmCn, consisting of two bis(p-oxyben
zoyl) units interconnected by a polymethylene segment containing n met
hylene groups and Ranked by two linear o-hydroxyalkyl segments contain
ing m methylene groups were reacted with 1,6-hexamethylenediisocyanate
(HDI) to give a new series of liquid-crystalline poly(ester-urethane)
s HDI-CmCn. All of the precursors CmCn exhibited a nematic phase, and
in two of them a smectic mesophase also occurred. Poly(ester-urethane)
s HDI-CmCn were semicrystalline and formed a monotropic mesophase. The
mesomorphic properties of the polymers were studied as a function of
their chemical structure by changing alternatively m or n. The effect
of the molecular weight of the polymers on the stability of the mesoph
ase was also investigated for various samples of poly(ester-urethane)
HDI-C6C6 (M(n) = 3000-22,000). It was found that a competition existed
between the tendencies of the polymer to crystallinity and liquid-cry
stallinity, and the molecular weight dependence of the crystallization
temperature determined the onset of a monotropic mesophase.