Measuring Refractive Indices of Nematic LC Elastomers
description
Transcript of Measuring Refractive Indices of Nematic LC Elastomers
![Page 1: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/1.jpg)
1
Measuring Refractive Indicesof Nematic LC Elastomers
Volodymyr Borshch
Research advisor:Professor Peter Palffy-Muhoray
25 August 2008
![Page 2: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/2.jpg)
2
Outline• Motivation • Nematic LC elastomer• Methods and previous results• Theory• Materials selection• Experimental setup• Obtained data• Conclusions• Acknowledgments
![Page 3: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/3.jpg)
3
Motivation
• Nematic LC Elastomers have bright future
• Not all physical properties are quite extensively described so far
• E.g. Refractive index
![Page 4: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/4.jpg)
4
Nematic LC elastomer
O OO
O
Mesogen
O
CH3H
CH3
Si O
CH3
SiH
CH3
Si H
85
CH3
Backbone
CH2
O
CH2
O
Crosslinker
From Israel Lazo presentation
![Page 5: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/5.jpg)
5
Methods
Israel Lazo presentation
![Page 6: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/6.jpg)
6
Yet another approach
• From Fresnel equations:
The main idea of the methodR=0
![Page 7: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/7.jpg)
7
High refractive index liquids
• Liquids at or near 20˚CRefractive index Material
1.627 Quinoline1.660 α-Monobromonaphthalene1.717 Mercury potassium iodide1.737 Methylene iodide1.78 Methylene iodide and sulphur (saturated)
1.793 Barium mercuric iodide aq.1.82 Potassium iodide and mercuric iodide aq.
1.868 Solutions of 35% by weight CH2I2, 31% SnI4, 16% AsI3, 8% SbI3 and 10% S
1.885 Hydrogen disulphide1.95 Phosphorus in carbon disulphide2.06 Yellow phosphorus 8 parts by weight + 1part sulphur + 1 methylene iodide2.2 Mercuric iodide in aniline or quinoline
Data from Kaye and Laby, Tables of Physical and Chemical Constants, 1959
Ionic liquids based on 1-alkyl-3-methylimidazolium cations
Most of them were either:- Highly toxic and poisonous- Not transparent- Not available A simple, cost-effective
and magnificent liquid was used – saturated
solution of NaIn = 1.496
![Page 8: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/8.jpg)
8
Experiment
HeNe
Rotating polarizer
Fish tank with immersed elastomer
Experimental setupMeasuring the reflectance
of the elastomer innormal incidence
λ/4 plate
detector
632.8 nmfilter
Referencebeam
Beam splitter
lens
Lock-inamplifier
detector
![Page 9: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/9.jpg)
9
y = -4.95494x + 7.94601R2 = 0.75418
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.410 1.420 1.430 1.440 1.450 1.460 1.470 1.480 1.490 1.500
refractive index, n
Refle
ctan
ce, R
(a.u
.)
perpendicular
Linear (perpendicular)
no measurement
• The polarization is perpendicular to the preferred director orientation n
elastomer with no strainbatch #71 (10% cross linkers)
Fitting and extrapolation gives n=1.60365 ±0.01633
The sample from batch #69 gave similar value n=1.53529
![Page 10: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/10.jpg)
10
y = -4.06398x + 6.67013R2 = 0.61900
00.10.20.30.40.50.60.70.80.9
11.11.2
1.410 1.420 1.430 1.440 1.450 1.460 1.470 1.480 1.490 1.500
refractive index, n
Refle
ctan
ce, R
(a.u
.)
parallel
Linear (parallel)
ne measurement
• The polarization is parallel to the preferred director orientation n
elastomer with no strainbatch #71 (10% cross linkers)
Fitting and extrapolation gives n =1.64128 ±0.03830
![Page 11: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/11.jpg)
11
Benefits and drawbacks of the method
• Looks simple
• Inhomogeneity of elastomer
• Scattering
![Page 12: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/12.jpg)
12
0 5 10 15 20 25 30 35 40
1.401.421.441.461.481.501.521.541.561.581.601.621.641.661.681.701.721.74
R
efra
ctiv
e In
dex
Strain (%)
ne Interferometer
no Interferometer
ne Brewster
no Brewster
![Page 13: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/13.jpg)
13
Conclusions
• The sample was different but the results agree with previous measurements
• The refractive indices need to be measured more accurately
• Future work: Generalized Ellipsometry• Need to measure inhomogeneity
![Page 14: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/14.jpg)
14
Acknowledgement
• Prof.Peter Palffy-Muhoray• Jake Fontana, Israel Lazo• Paul Luchette, Michele Fontana• Jeremy Neal, Sabrina Relaix• Rafael Zola
![Page 15: Measuring Refractive Indices of Nematic LC Elastomers](https://reader036.fdocuments.net/reader036/viewer/2022062410/56816678550346895dda1601/html5/thumbnails/15.jpg)
15
Thank you !