Study of chiral molecular diffusion in anisotropic liquids

Karen Allahverdyan and Tigran Galstian

Center for Optics, Photonics and Laser (COPL),Department of Physics, Engineering Physics and Optics, Laval University,Pav. d’Optique-Photonique, 2375 Rue de la Terrasse, Québec, Canada G1V 0A6

Presented by: K. Allahverdyankaren.allahverdyan.1@ulaval.ca

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Chirality

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The presence of chiral compound in liquids

Reflective LC displays, thermometers (temperature distribution maps), circular polarizers, dichroic filters& mirrors… Smart windows…

Photonic band gap structures

Optical activity • Manipulation of light polarization & path• Precise measurement of concentration • Various biomedical applications, drugs …• etc.

In isotropic liquids

Periodic structure• 1D photonic crystal• Tunable Bragg gratings• Selective reflection• Etc.

In anisotropic liquids

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Chiral compound in anisotropic liquids

NLC CLC

Chiral dopant

Boundary conditionsStrong

rubbing

Chiral dopant

Weak

Chiral dopant

5

6

Chiral droplet in NLC

Strong boundary conditions vs Weak boundary conditions

For given materials, the temperature is the major factor acting on the diffusion dynamics.

𝑣 1𝑘𝑇

7

15min

Chiral droplet in NLC10h

0.5mm

18h

Rubbed(strong)

Non-rubbed(weak)

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r

d

9

The evolution of fringes

0 5 100102030405060708090100110120

Weak

d(um

)

Time (hour)

Strong

0 2 4 6 8 10 12

100

200

300

400

500

Weak

r (um

)

Time (hour)

Strong

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Azobenzene droplet in NLC

0.5mm

Rubbed(strong)

Non-rubbed(weak)

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The diffusion dynamics

-200 -100 0 100 2000

20

40

60

80

100

120

140

160

20h

4h

15min

Distance (a.u.)

Blue

from

RG

B

Distribution of azo. concentration

The diffusion processes are similar in both cases (strong or weak boundaries)

The diffusion is faster in the rubbing direction.

0 50 100 150 200 250 3000

5

10

15

20

25

30

35

Weak

Strong(parallel)

Diffu

sion

dep

th (a

.u)

Time (min)

Strong(perp.)

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Agglomeration of chiral molecules

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• The diffusion of chiral molecules in anisotropic liquids is different then in isotropic liquids.

• The boundary conditions can be used to control the diffusion dynamics in anisotropic liquids.

• The differences and the possibility of control is due to collective organizing tendency of liquid crystals.

Conclusion

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