Home
Resources
Publications
Chiral smectic-A and smectic-C Phases With De Vries Characteristics

Chiral smectic-A and smectic-C Phases With De Vries Characteristics

Neelam Yadav, V P Panov, V Swaminathan, S P Sreenilayam, J K Vij, T S Perova, R Dhar, A Panov, D Rodriguez-Lojo, P J Stevenson

Phys Rev E. 2017 Jun;95(6-1):062704.

PMID: 28709233

Abstract:

Infrared and dielectric spectroscopic techniques are used to investigate the characteristics of two chiral smectics, namely, 1,1,3,3,5,5,5-heptamethyltrisiloxane 1-[4^{'}-(undecyl-1-oxy)-4-biphenyl(S,S)-2-chloro-3-methylpentanoate] (MSi_{3}MR_{11}) and tricarbosilane-hexyloxy-benzoic acid (S)-4'-(1-methyl-hexyloxy)-3'-nitro-biphenyl-4-yl ester (W599). The orientational features and the field dependencies of the apparent tilt angle and the dichroic ratio for homogeneous planar-aligned samples were calculated from the absorbance profiles obtained at different temperatures especially in the smectic-A* phase of these liquid crystals. The dichroic ratios of the C-C phenyl ring stretching vibrations were considered for the determination of the tilt angle at different temperatures and different voltages. The low values of the order parameter obtained with and without an electric field applied across the cell in the Sm-A^{*} phase for both smectics are consistent with the de Vries concept. The generalized Langevin-Debye model introduced in the literature for explaining the electro-optical response has been applied to the results from infrared spectroscopy. The results show that the dipole moment of the tilt-correlated domain diverges as the transition temperature from Sm-A^{*} to Sm-C^{*} is approached. The Debye-Langevin model is found to be extremely effective in confirming some of the conclusions of the de Vries chiral smectics and gives additional results on the order parameter and the dichroic ratio as a function of the field across the cell. Dielectric spectroscopy finds large dipolar fluctuations in the Sm-A^{*} phase for both compounds and again these confirm their de Vries behavior.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1873887-B	1,1,1,3,5,5,5-Heptamethyltrisiloxane		1873-88-7	Price

As a specialist in analytical chemical Products, Alfa Chemistry offers consumers a wealth of raw materials and a full range of technologies and services.

QUICK LINKS

HEADQUARTERS

Tel:

Fax:

Email: