Phase transition and dewetting of a 5CB liquid crystal thin film on a topographically patterned substrate

Dhara, Palash; Mukherjee, Rabibrata

doi:10.1039/c9ra02552a

Cited by 15 publications

(16 citation statements)

References 58 publications

(81 reference statements)

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“…The isotropic phase of pure 5CB was fully converted into the nematic phase at T < T IN (which differed from the phase separation behavior of the DMP/5CB mixture). This observation agrees with the behavior of bulk 5CB reported in literature, with the reported T IN being in a range of 34.0-35.3 ºC [7][8][9][10][11] .…”

Section: -1 Phase Transition Temperaturesupporting

confidence: 92%

Thermodynamic Effect on Viscosity and Density of a Mixture of 4-Cyano-4′-pentylbiphenyl (5CB) with Dilute Dimethyl Phthalate (DMP)

Shimada

Watanabe

2020

J. Soc. Rheol., Jpn

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Density ρ and viscosity η were examined for 4-cyano-4′-pentylbiphenyl (5CB) and its mixture with dilute dimethyl phthalate (DMP; w DMP = 3.1 wt%). The mixture was in an isotropic 1-phase state at temperatures T > T IN * (≅ 27 ºC), and exhibited the phase separation into the isotropic and nematic phases at T IN *. Pure 5CB exhibited the (well known) fi rst-order isotropic-to-nematic transition characterized by discontinuous changes of ρ and η at T IN (≅ 35.0 ºC), whereas no discontinuous changes were observed for the mixture at T IN * because only a small amount of the nematic phase was created at T IN *. The discontinuity was expected for the local density and viscosity in the nematic phase at T IN * and, in this sense, no essential difference was noted for that phase in the 5CB and DMP/5CB systems. Nevertheless, a characteristic difference was found in the isotropic 1-phase state. These systems commonly exhibited simple asymptotic behavior at suffi ciently high T, linear thermal expansion of the specifi c volume 1/ρ and Eyring/Andrade-type T dependence of the kinematic viscosity, ν = η/ρ. Positive deviation from these asymptotes was noted for both systems on cooling toward respective transition temperatures, T IN and T IN *, but in a considerably wide range of T (up to T IN *+10K or more) for the DMP/5CB mixture whereas only in a close vicinity of T IN (within a few K) for pure 5CB. This difference is related to the concentration fl uctuation (due to the soft, osmotic interaction of molecules) emerging only in the mixture.

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Section: -1 Phase Transition Temperaturesupporting

confidence: 92%

Thermodynamic Effect on Viscosity and Density of a Mixture of 4-Cyano-4′-pentylbiphenyl (5CB) with Dilute Dimethyl Phthalate (DMP)

Shimada

Watanabe

2020

J. Soc. Rheol., Jpn

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“…For instance, γnormalIN was measured for the nematic MBBA as γnormalIN=10−5 normalN normalm−1 [64], which is three orders of magnitude smaller than a typical isotropic interfacial tension for a gas–nematic interface γnormalGN [57]. Such a situation could be realized experimentally by using controlled heating and cooling of regions of a substrate coated in a nematic film [34,65].…”

Section: Discussionmentioning

confidence: 99%

Young and Young–Laplace equations for a static ridge of nematic liquid crystal, and transitions between equilibrium states

et al. 2022

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Motivated by the need for greater understanding of systems that involve interfaces between a nematic liquid crystal, a solid substrate and a passive gas that include nematic–substrate–gas three-phase contact lines, we analyse a two-dimensional static ridge of nematic resting on a solid substrate in an atmosphere of passive gas. Specifically, we obtain the first complete theoretical description for this system, including nematic Young and Young–Laplace equations, and then, making the assumption that anchoring breaking occurs in regions adjacent to the contact lines, we use the nematic Young equations to determine the continuous and discontinuous transitions that occur between the equilibrium states of complete wetting, partial wetting and complete dewetting. In particular, in addition to continuous transitions analogous to those that occur in the classical case of an isotropic liquid, we find a variety of discontinuous transitions, as well as contact-angle hysteresis, and regions of parameter space in which there exist multiple partial wetting states that do not occur in the classical case.

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“…For instance, γ IN was measured for the nematic MBBA as γ IN = 10 −5 Nm −1 [62], which is three orders of magnitude smaller than typical isotropic interfacial tension for a gas-nematic interface γ GN [54]. Such a situation could be realised experimentally by using controlled heating and cooling of regions of a substrate coated in a nematic film [31,63].…”

Section: Discussionmentioning

confidence: 99%

Young and Young--Laplace equations for a static ridge of nematic liquid crystal, and transitions between equilibrium states

Cousins,

Duffy,

Wilson

et al. 2021

Preprint

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Motivated by the need for greater understanding of systems that involve interfaces between a nematic liquid crystal, a solid substrate, and a passive gas that includes nematic-substrate-gas three-phase contact lines, we analyse a two-dimensional static ridge of nematic resting on a solid substrate in an atmosphere of passive gas. Specifically, we obtain the first complete theoretical description for this system, including nematic Young and Young-Laplace equations, and then, under the assumption that anchoring breaking occurs in regions adjacent to the contact lines, we use the nematic Young equations to determine the continuous and discontinuous transitions that occur between the equilibrium states of complete wetting, partial wetting, and complete dewetting.In particular, in addition to continuous transitions analogous to those that occur in the classical case of an isotropic liquid, we find a variety of discontinuous transitions, as well as contact-angle hysteresis, and regions of parameter space in which there exist multiple partial wetting states that do not occur in the classical case.

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Phase transition and dewetting of a 5CB liquid crystal thin film on a topographically patterned substrate

Abstract: Thermally induced nematic to isotropic (N–I) phase transition and dewetting of 5CB liquid crystal thin films on flat and topographically patterned substrates.

Cited by 15 publications

References 58 publications

Thermodynamic Effect on Viscosity and Density of a Mixture of 4-Cyano-4′-pentylbiphenyl (5CB) with Dilute Dimethyl Phthalate (DMP)

Thermodynamic Effect on Viscosity and Density of a Mixture of 4-Cyano-4′-pentylbiphenyl (5CB) with Dilute Dimethyl Phthalate (DMP)

Young and Young–Laplace equations for a static ridge of nematic liquid crystal, and transitions between equilibrium states

Young and Young--Laplace equations for a static ridge of nematic liquid crystal, and transitions between equilibrium states

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