TY - JOUR

T1 - Physical model for temperature-dependent dielectric properties of anisotropic nematic liquid crystals

AU - Ranjkesh, Amid

AU - Moghadam, Mohammad

AU - Choi, Jun Chan

AU - Kim, Byeonggon

AU - Ko, Jeonghoon

AU - Zakerhamidi, Mohammad Sadegh

AU - Kim, Hak Rin

N1 - Publisher Copyright:
© 2018 the Owner Societies.

PY - 2018

Y1 - 2018

N2 - We derived a new analytic physical model for describing the temperature-dependent dielectric permittivities ϵe(T) and ϵo(T) in anisotropic mesophase molecules of nematic liquid crystals (NLCs). These temperature-dependent dielectric properties of NLCs could be explained by a six-parameter dielectric permittivity model, where the analytic dielectric permittivity curves of ϵe(T), ϵo(T), and Δϵ(T) from the model using the six parameters ϵ∗, Aϵ, Bϵ, (Δϵ)o, λϵ, and T∗ showed excellent agreement with experimental data. The six-parameter dielectric permittivity model was compared to the conventional four-parameter refractive index model. To systematically investigate the temperature-dependent properties of the refractive indices (ne(T) and no(T)) and dielectric permittivities according to the molecular structure of the NLCs, four similar types of fluorinated phenyl bicyclohexane NLCs were selected. Using the presented models, the temperature-dependent behaviour of these four fluorinated NLCs was discussed, according to the molecular length of the alkyl chains and the positions of the fluorine substituents. In particular, two fitting equations for the temperature-dependent properties of threshold voltage and splay elastic LC constant could also be developed using the physical coefficients extracted from the six-parameter dielectric permittivity model, and these equations coincided well with experimental results.

AB - We derived a new analytic physical model for describing the temperature-dependent dielectric permittivities ϵe(T) and ϵo(T) in anisotropic mesophase molecules of nematic liquid crystals (NLCs). These temperature-dependent dielectric properties of NLCs could be explained by a six-parameter dielectric permittivity model, where the analytic dielectric permittivity curves of ϵe(T), ϵo(T), and Δϵ(T) from the model using the six parameters ϵ∗, Aϵ, Bϵ, (Δϵ)o, λϵ, and T∗ showed excellent agreement with experimental data. The six-parameter dielectric permittivity model was compared to the conventional four-parameter refractive index model. To systematically investigate the temperature-dependent properties of the refractive indices (ne(T) and no(T)) and dielectric permittivities according to the molecular structure of the NLCs, four similar types of fluorinated phenyl bicyclohexane NLCs were selected. Using the presented models, the temperature-dependent behaviour of these four fluorinated NLCs was discussed, according to the molecular length of the alkyl chains and the positions of the fluorine substituents. In particular, two fitting equations for the temperature-dependent properties of threshold voltage and splay elastic LC constant could also be developed using the physical coefficients extracted from the six-parameter dielectric permittivity model, and these equations coincided well with experimental results.

UR - http://www.scopus.com/inward/record.url?scp=85050467164&partnerID=8YFLogxK

U2 - 10.1039/c8cp01577e

DO - 10.1039/c8cp01577e

M3 - Article

C2 - 29856453

AN - SCOPUS:85050467164

SN - 1463-9076

VL - 20

SP - 19294

EP - 19306

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 29

ER -