Dielectric spectroscopy of the SmQ* phase

Autor:	Miroslav Kašpar, Věra Hamplová, Paweł Perkowski, Wiktor Piecek, K. Ogrodnik, Alexej Bubnov
Rok vydání:	2011
Předmět:	Biphenyl Phase transition Materials science Isotropy Relaxation (NMR) Molecular axis Dielectric spectroscopy chemistry.chemical_compound Crystallography Nuclear magnetic resonance chemistry Liquid crystal Phase (matter) General Materials Science Instrumentation
Zdroj:	Phase Transitions. 84:1098-1107
ISSN:	1029-0338 0141-1594
DOI:	10.1080/01411594.2011.580432
Popis:	Liquid crystal possessing two biphenyl moieties in the molecular core and lateral chlorine substitution far from the chiral chain has been studied by dielectric spectroscopy. On cooling from the isotropic phase, the material possesses the frustrated smectic Q* (SmQ*) and SmCA* phases. It has been confirmed by dielectric spectroscopy that the SmQ* phase can be related to the SmCA* anti-ferroelectric phase. However, only one relaxation process has been observed in the SmQ* phase, while in the SmCA*, two relaxations are clearly detectable. It seems that the mode found in the SmQ* can be connected with high-frequency anti-phase mode observed in the SmCA* phase. Its relaxation frequency is similar to PH relaxation frequency, but is weaker. The same relaxation has been observed even a few degrees above the SmQ*–Iso phase transition. Another explanation for the mode detected in SmQ* and isotropic phases can be molecular motions around short molecular axis.
Databáze:	OpenAIRE
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