Dynamics and Structure of Smectic Liquid Crystal Multilayers at the Air/Water Interface

P.Basnet *

L.Zou *

J.Wang *V.Beleva *A.Bernoff † J.Alexander ¤

J.A.Mann Jr. ‡

E.K.Mann*

* Dept. of Physics, Kent State University,Kent ,OH 44242, † Dept.of Mathematics, Harvey Mudd College, Claremont, CA 91711, ¤ Dept. of Mathematics, Case Western Reserve University, Cleveland OH 44106, ‡ Dept. of Chemical Eng., Case Western Reserve University, Cleveland OH 44106

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Water

Goal: Characterize boundaries between domainswith line tension

8CB Molecule

[Ref] M.N.G. de Mul, J.A. Mann Jr.- Langmuir(1994, 1998)

[Ref]

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Why interested?line tension- helps determine equilibrium size and shape distribution for domains,- helps determine dynamics and stability of such domains- At this time, cannot be either predicted or controlled, unlike surface tension- few systematic experimental studies exist.

Previous work J. Lauger, C.R. Robertson, C.W. Frank, G.G. Fuller- Langmuir,12(1996) - estimated line tension for the lowest two layers,- found a factor of 10 difference

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Surface pressure-area isotherm for 8CB

A [nm2/molecule]

0.0 0.1 0.2 0.3 0.4 0.5 0.6

[m

N/m

]

0

1

2

3

4

5

6

7

T = 25 C, 10 mm/min

1

23

3

1

2

5

[Ref]

[Ref] Xue, Jung, M.W. Kim- PRL (1992)M.N.G. de Mul & J. A. Mann Jr.- Langmuir (1994)M.N.G. de Mul & J. A. Mann Jr.- Langmuir (19980)

Parallel band cell for simple shear flow

StagnationLine

Fig. b

Two dimensional, extensional flow generated by using

four-roll-mill

Fig. a

StagnationPoint

[Ref] G.G .Fuller- Current opinion in Colloid & Interface Science 1997

[Ref]

[Ref]

Driving force: Line tension

Experimental Techniques for domain deformation

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Relaxation of deformed domain

7

10

Reflectivity & Thickness of Domains

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Trilayer /

molayer

1 multi l

ayer / trila

yer

Several

multilayer

s / tril

ayer

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∆L

a

b

a. Collapse of an 8CB monolayer to trilayer.

b. Collapse of a trilayer to a nine-layered stacked interdigitated bilayer structure.

Collapse of Layers to Higher Multilayers

[Ref] M.N.G. de Mul & J. A. Mann Jr.-Langmuir 1994,10

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Acknowledgement

Elizabeth K. MannLu ZouJi WangV. BelevaA. BernoffJ. A. Mann Jr.Supported by NSF, Grant No. 9984304

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