We synthesised a series of rod-like mesogens with a (S)-2-methylbutyl-(S)-lactate unit in the chiral chain that exhibited extremely wide temperature ranges in the TGBA and TGBC* phases. TGB phases were identified, based on typical textures in confined samples and in free-standing films, by Grandjean-Cano texture and by NMR studies on a deuterium-labelled isotopomer. A sufficiently high electric or magnetic field transformed the TGBA and TGBC* phases into their respective SmA and SmC* phases, the TGB structures being restored within some 20-30 minutes. Therefore values of the spontaneous polarisation and spontaneous tilt angle, when measured under a sufficiently high field, gave evidence of the properties of the SmC* phase. Temperature dependencies of relaxation frequency, dielectric strength, selective reflection and layer spacing showed anomalies at a certain temperature within the TGBC* phase range. Also, changes in textures, as well as in 2H-NMR spectra, occurred at this same temperature. These results suggest the existence of two TGBC* phases.
|Autori:||V. NOVOTNA; M. KASPAR; DOMENICI V; V. HAMPLOVA; M. GLOGAROVA; P. BILKOVA; D. POCIECHA|
|Titolo:||Synthesis and mesomorphic properties of new compounds exhibiting TGBA and TGBC liquid crystalline phases|
|Anno del prodotto:||2008|
|Digital Object Identifier (DOI):||10.1080/02678290701862215|
|Appare nelle tipologie:||1.1 Articolo in rivista|