Synthesis and liquid-crystalline properties of thermotropic poly(ester-urethane)s

✍ Scribed by A.S. Angeloni; M. Laus; E. Chiellini; G. Galli; O. Francescangeli

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 617 KB
• Volume: 31
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(94)00163-4

✦ Synopsis

Seven new mesogenic diol monomers CmCn, consisting of two bis(p-oxybenzoyl) units interconnected by a polymethylene segment containing n methylene groups and flanked by two linear w-hydroxyalkyl segments containing m methylene groups were reacted with l$-hexamethylenediisocyanate (HIN) to give a new series of liquid-crystalline poly(ester-urethane)s HDICmCn. 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) HDK6C6 (M, = 300%22,000). It was found that a competition existed between the tendencies of the polymer to crystallinity and liquidcrystallinity, and the molecular weight dependence of the crystallization temperature determined the onset of a monotropic mesophase.