Dielectric spectroscopy of liquid crystals in smectic, nematic, and isotropic phases confined in random porous media

1998 ◽  
Vol 58 (2) ◽  
pp. 2001-2010 ◽  
Author(s):  
G. P. Sinha ◽  
F. M. Aliev
Keyword(s):  
Porous Media ◽  
Liquid Crystals ◽  
Dielectric Spectroscopy ◽  
Random Porous Media

Dielectric Relaxation in a Deeply Supercooled Liquid Crystals Confined in Random Porous Media

1998 ◽  
Vol 543 ◽  
Author(s):  
G. P. Sinha ◽  
F. M. Aliev
Keyword(s):  
Porous Media ◽  
Relaxation Time ◽  
Liquid Crystals ◽  
Dynamical Behavior ◽  
Broad Band ◽  
Pore Wall ◽  
Relaxation Processes ◽  
Main Mode ◽  
Supercooled State ◽  
Random Porous Media

AbstractLiquid crystals (LCs)—pentylcyanobiphenyl (5CB) and octylcyanobiphenyl (8CB)—were confined in random porous media with narrow pores of mean size equal to 100 Å and investigated by means of broad band dielectric spectroscopy in deeply supercooled state. In liquid crystalline phases, bulk 5CB and 8CB have two dielectrically active modes. The main mode with the relaxation time τ ∼ 10”8s is due to the rotation of molecules about their short axis, and the secondary mode is due to the tumbling motion of molecules with the relaxation time ツ ∼ 10”10s. Bulk 5CB and 8CB are nonglass formers and they crystallize at cooling. The confinement strongly influences the dynamical behavior of LCs and is resulted in qualitative changes in their properties. Deep supercooling of LCs in pores up to ∼ 150 degrees below the bulk crystallization temperature was observed. The relaxation rate of the process due to the molecular rotation in deeply supercooled state is slower than at the temperatures corresponding to nematic phase by many orders of magnitude. This slowing down is accompanied by anomalous broadening of the dielectric spectra.Other new properties observed in confined LCs are two low frequency relaxation processes absent in bulk LCs. One of these processes is due to the molecular relaxation in the surface layers at liquid crystal-solid pore wall interface. The second process is probably a collective mode due to the relaxation of the surface induced polarization. The collective process due to surface polarization and the surface molecular mode show features typical for glass formers.

scholarly journals Evaluation of the path integral for flow through random porous media

2018 ◽  
Vol 97 (4) ◽  
Author(s):  
Marise J. E. Westbroek ◽  
Gil-Arnaud Coche ◽  
Peter R. King ◽  
Dimitri D. Vvedensky
Keyword(s):  
Porous Media ◽  
Path Integral ◽  
Flow Through ◽  
Random Porous Media

Flows in random porous media: effective models

2003 ◽  
Vol 30 (4) ◽  
pp. 271-288 ◽  
Author(s):  
J.J. Telega ◽  
W.R. Bielski
Keyword(s):  
Porous Media ◽  
Random Porous Media ◽  
Effective Models

scholarly journals Statistics of highly heterogeneous flow fields confined to three-dimensional random porous media

2016 ◽  
Vol 93 (1) ◽  
Author(s):  
C. Jin ◽  
P. A. Langston ◽  
G. E. Pavlovskaya ◽  
M. R. Hall ◽  
S. P. Rigby
Keyword(s):  
Porous Media ◽  
Three Dimensional ◽  
Flow Fields ◽  
Heterogeneous Flow ◽  
Random Porous Media

Two-phase flow in correlated pore-throat random porous media

2002 ◽  
Vol 11 (4) ◽  
pp. 358-365 ◽  
Author(s):  
Tian Ju-Ping ◽  
Yao Kai-Lun
Keyword(s):  
Porous Media ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Pore Throat ◽  
Two Phase ◽  
Random Porous Media
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