The peculiar liquid crystalline behavior of two poly(urethane-ester)s TDI-C6C4 and TDI-C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI-C6C8 and of one cybotactic nematic mesophase in TDI-C6C4. IR spectroscopy indicates that different hydrogen bonded and non-bonded structures occur with varying temperature. The transition from the nematic cybotactic mesophase to the nematic mesophase, or to the isotropic phase, is accompanied by a substantial decrease of the strength of the hydrogen bonds. This is also reflected in the dynamic mechanical behavior of these poly(urethane-ester)s which is similar to the one of slightly crosslinked thermoreversible networks.
The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethane-ester)s / M., Laus; A. S., Angeloni; Francescangeli, Oriano; G., Galli; E., Chiellini. - In: MACROMOLECULAR SYMPOSIA. - ISSN 1022-1360. - 117:(1997), pp. 275-280. [10.1002/masy.19971170131]
The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethane-ester)s
FRANCESCANGELI, ORIANO;
1997-01-01
Abstract
The peculiar liquid crystalline behavior of two poly(urethane-ester)s TDI-C6C4 and TDI-C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI-C6C8 and of one cybotactic nematic mesophase in TDI-C6C4. IR spectroscopy indicates that different hydrogen bonded and non-bonded structures occur with varying temperature. The transition from the nematic cybotactic mesophase to the nematic mesophase, or to the isotropic phase, is accompanied by a substantial decrease of the strength of the hydrogen bonds. This is also reflected in the dynamic mechanical behavior of these poly(urethane-ester)s which is similar to the one of slightly crosslinked thermoreversible networks.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
