Effect of magnetic field on molecular orientation of nematic liquid crystalline polymers under simple shear flow

Fu, Shufang; Tsuji, Tomohiro; Chono, Shigeomi

doi:10.1122/1.2837113

Cited by 8 publications

(10 citation statements)

References 30 publications

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“…also is found at low shear rate region. The sign changes of the time‐averaged $\bar N_1^* \,$ and $\bar N_2^*$ are completely opposite with those results obtained for rodlike LCPs by the Refs 18. and19.…”

Section: Discussioncontrasting

confidence: 67%

“…When only the shear rate is imposed, the similarity with the various regimes of rodlike LCPs in the shear flow, which is in good agreement with the conclusions presented by Farhoudi and Rey,27 is obtained. Due to the moment caused by the magnetic field stronger than that caused by the shear flow the new aligning state defined in the Ref 18. also is found at low shear rate region.…”

Section: Discussionmentioning

confidence: 65%

“…When the magnetic field is imposed, for example H

_{italicx}^{*}

= 0.5 × 10 −6 , the decrease period becomes longer. And once a critical magnetic field strength is arrived, H

_{italicx}^{*}

= 0.9 × 10 −6 , ϕ m no longer changes with time and the system shows an aligning like behavior, which is called the new aligning behavior defined in Ref 18…”

Section: Resultsmentioning

confidence: 99%

“…If one can freely control the molecular orientation configuration, the processing optimization may become much simpler. It is well known that the electric or magnetic field imposed on the rodlike LCPs results in the improvement of performance for LCP products 18, 19. Some experiments,20, 21 such as the uses of surface effect and shear flow, were made to obtain alignment phase of discotic LCs.…”

Section: Introductionmentioning

confidence: 99%

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Effect of magnetic field on discotic nematic liquid crystalline polymers under simple shear flow

Jing-Bai

Wang

2012

J of Applied Polymer Sci

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The effect of magnetic field on the discotic nematic liquid crystalline polymers (LCPs) is analyzed with the extended Doi theory, in which the molecular shape parameter (β) is defined at −1.0. The evolution equation for the probability function of the discotic nematic LCP molecules is solved without any closure approximations. The transition among flow‐orientation modes, such as tumbling, wagging, and aligning defined similar to the rodlike LCPs, is strongly affected by the magnetic fields. The new aligning flow‐orientation mode observed for the rodlike LCPs under magnetic fields also can be investigated in the lower shear rate region. On the other hand, the effect of magnetic fields parallel to the x‐ and y‐axis on the time‐averaged first and second normal stress differences ( $\bar N_1^*$, $\bar N_2^*$) are also studied. It can be seen that the shear rate regions of the sign changes of $\bar N_1^*$, $\bar N_2^*$ are completely contrary to those conclusions achieved for the rodlike LCPs. In addition, the absolute values of $\bar \eta ^*$ increase with the magnetic field strength in the lower shear rate range owing to the new aligning flow‐orientation mode. Finally, the flow‐phase diagram versus β is also discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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Section: Discussioncontrasting

confidence: 67%

Section: Discussionmentioning

confidence: 65%

“…When the magnetic field is imposed, for example H

_{italicx}^{*}

= 0.5 × 10 −6 , the decrease period becomes longer. And once a critical magnetic field strength is arrived, H

_{italicx}^{*}

= 0.9 × 10 −6 , ϕ m no longer changes with time and the system shows an aligning like behavior, which is called the new aligning behavior defined in Ref 18…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of magnetic field on discotic nematic liquid crystalline polymers under simple shear flow

Jing-Bai

Wang

2012

J of Applied Polymer Sci

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“…The purposes of this work are to investigate the effect of magnetic field on the first and second normal stress differences N 1 , N 2 , and the shear stress σ xy in LCPs processing with the Doi theory solved without any closure approximations. Recently, in the studies,15, 16 the effect of magnetic fields on molecular configuration of LCPs under simple shear flows for the in‐plane and out‐plane cases are numerically analyzed using the Doi‐Hess equation. The strength of LCPs can be tailored by applying the appropriate magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Effects of magnetic field on shear stress of nematic liquid crystalline polymer under simple shear flow

Wang

2010

J Polym Sci B Polym Phys

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The effect of magnetic fields on the shear stress of liquid crystalline polymers (LCPs) under shear flows is numerically analyzed using the Doi theory. The evolution equation for the probability density of LCP molecules is directly solved without any closure approximations. When the magnetic field is imposed on the LCPs along the shear flow, the low-shear rate plateau of the time-averaged generalized viscosity g Ã ð¼ r Ã xy = _ c Ã Þ disappears, which is due to the manner of the new aligning mode observed by Fu et al. The negative first normal stress difference N Ã 1 becomes opposite in all the shear rate regimes with the disappearance of periodic oscillations. For the magnetic field parallel to the velocity gradient direction, the more complicated sign changes of N Ã 1 is investigated because of the moment caused by the magnetic field vertical to the one caused by the shear flow. The ratio N Ã 2 = N Ã1 increases with the increasing magnetic field strength. Finally, when the molecular shape parameter is considered as 0.9, the similar discussions are achieved according to the phase diagram among tumbling, wagging, and aligning modes versus the magnetic field strength.

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Electrically-driven modulation of flow patterns in liquid crystal microfludics

Fedorowicz,

Prosser

2024

Sci Rep

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The flow of liquid crystals in the presence of electric fields is investigated as a possible means of flow control. The Beris-Edwards model is coupled to a free energy incorporating electric field effects. Simulations are conducted in straight channels and in junctions. Our findings reveal that local flow mediation can be achieved by the application of spatially varying electric fields. In rectangular straight channels, we report a two-stream velocity profile arising in response to the imposed electric field. Furthermore, we observe that the flow rate in each stream scales inversely with the Miesowicz viscosities, leading to the confinement of 70% of the throughput to one half of the channel. Similar flow partitioning is also demonstrated in channel junction geometries, where we show that using external fields provides a novel avenue for flow modulation in microfluidic circuits.

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Effect of magnetic field on molecular orientation of nematic liquid crystalline polymers under simple shear flow

Cited by 8 publications

References 30 publications

Effect of magnetic field on discotic nematic liquid crystalline polymers under simple shear flow

Effect of magnetic field on discotic nematic liquid crystalline polymers under simple shear flow

Effects of magnetic field on shear stress of nematic liquid crystalline polymer under simple shear flow

Electrically-driven modulation of flow patterns in liquid crystal microfludics

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