n x-ray investigation on powder specimens and stretched oriented fibers of poly(urethane-ester)s s TDI-CmCn, derived from various mesogenic alkylene di[4-(omega-hydroxyalkyloxy-4-oxybenzoyl)oxybenzoate]s (CmCn; m = 2, 4, or 6, and n = 4, 6, 8, or 10) and 2,4-toluene-diisocyanate (TDI), is reported. Evidence is provided for the formation of two different nematic mesophases in the polymers, namely a cybotactic nematic and a conventional nematic mesophase. Whereas samples TDI-C2C6, TDI-C6C4, and TDI-C6C10 formed one cybotactic nematic mesophase, samples TDI-C4C6, TDI-C6C6, and TDI-C6C8 exhibited both cybotactic nematic and conventional nematic mesophases in a sequence with increasing temperature, which were connected by a first-order transition. The analysis of the various features of the small-angle x-ray diffraction patterns indicates that two structural arrangements, namely smectic C-like and conventional nematic structures, coexist inside the cybotactic nematic mesophase of these poly(urethane-ester)s.
An X-ray Diffraction Study of the Different Nematic Mesophases of Liquid-Crystalline Poly(urethane-ester)s / Francescangeli, Oriano; B., Yang; M., Laus; A. S., Angeloni; G., Galli; E., Chiellini. - In: JOURNAL OF POLYMER SCIENCE. PART B, POLYMER PHYSICS. - ISSN 0887-6266. - 33 (4):(1995), pp. 699-705-699-705. [10.1002/polb.1995.090330419]
An X-ray Diffraction Study of the Different Nematic Mesophases of Liquid-Crystalline Poly(urethane-ester)s
FRANCESCANGELI, ORIANO;
1995-01-01
Abstract
n x-ray investigation on powder specimens and stretched oriented fibers of poly(urethane-ester)s s TDI-CmCn, derived from various mesogenic alkylene di[4-(omega-hydroxyalkyloxy-4-oxybenzoyl)oxybenzoate]s (CmCn; m = 2, 4, or 6, and n = 4, 6, 8, or 10) and 2,4-toluene-diisocyanate (TDI), is reported. Evidence is provided for the formation of two different nematic mesophases in the polymers, namely a cybotactic nematic and a conventional nematic mesophase. Whereas samples TDI-C2C6, TDI-C6C4, and TDI-C6C10 formed one cybotactic nematic mesophase, samples TDI-C4C6, TDI-C6C6, and TDI-C6C8 exhibited both cybotactic nematic and conventional nematic mesophases in a sequence with increasing temperature, which were connected by a first-order transition. The analysis of the various features of the small-angle x-ray diffraction patterns indicates that two structural arrangements, namely smectic C-like and conventional nematic structures, coexist inside the cybotactic nematic mesophase of these poly(urethane-ester)s.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
