Seven new mesogenic diol monomers CmCn, consisting of two bis(p-oxybenzoyl) units interconnected by a polymethylene segment containing n methylene groups and Ranked by two linear o-hydroxyalkyl segments containing 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 mesophase 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-crystallinity, and the molecular weight dependence of the crystallization temperature determined the onset of a monotropic mesophase.
Synthesis and liquid-crystalline properties of thermotropic poly(ester-urethane)s / A. S., Angeloni; M., Laus; E., Chiellini; G., Galli; Francescangeli, Oriano. - In: EUROPEAN POLYMER JOURNAL. - ISSN 0014-3057. - 31 (3):(1995), pp. 253-258. [10.1016/0014-3057(94)00163-4]
Synthesis and liquid-crystalline properties of thermotropic poly(ester-urethane)s
FRANCESCANGELI, ORIANO
1995-01-01
Abstract
Seven new mesogenic diol monomers CmCn, consisting of two bis(p-oxybenzoyl) units interconnected by a polymethylene segment containing n methylene groups and Ranked by two linear o-hydroxyalkyl segments containing 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 mesophase 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-crystallinity, and the molecular weight dependence of the crystallization temperature determined the onset of a monotropic mesophase.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.