1
Bending Modulus of MicroemulsionsUsing Neutron Spin Echo Spectrometer
Group AMohan babu Boggara
Xihua ZhaoZheng Yi
Joel HeltonElvis ZambranoLillian FrazierNina VerdalJiaqiang Yan
Outline
• Colloidal systems (Microemulsions)
• Neutron Spin Echo Spectrometer
• Data Analysis
• Results and Discussion
2
H2O
C6H14Surfactant
Colloidal systems
H2O
SurfactantCylindrical micelles Lamellae
H2O
Vesicles
Properties of the surfactant film:
• Interfacial tension• Lateral elasticity• Spontaneous curvature• Bending elasticity• Saddle splay elasticity
D2O(deuterated)
C6D14(deuterated)AOT
(hydrogenated)AOT/D2O/d-Hexane –5.1/2.5/92.4 v/v% φ= 0.077= 7.7%
Neutron Spin Echo• δδδδE=10-5–10-2 meV (very small!!!) -- Fourier time of 10 ps to 100 ns• Q = 0.05- 1.25 Å-1 (Resolution : +/- 0.02 Å-1)
• Cold neutrons: λ = 5 – 12 Å, E = 0.5 – 3.3 meV
�
S
B B
�/2 flipper �/2 flipper� flipper
3
NSE-Data Reduction and Analysis
Carbopack—Fully Elastic scattering (For Resolution Measurement)Background—SolventSample– Quasi-elastic ScatteringMicro emulsion information– Average size and polydispersity from SANS
4
Intermediate Scattering function
(Isample-Ibackground)/IResolution
Fourier time
Q
( )( ) ( )[ ]tQQD
tQItQI 2exp
0,, −==
Diffusion Coeff. of Droplet Deformation
( )
( )[ ] ( )���
��� +
+=2
2022
002
22022
54
5)(
aQRfQRjQ
aQRfDQD treff
π
λ
5
Bending Modulus of Elasticity
���
�
���
� ++=η
ηηηλπ 3
32'23481 3
022R
p
Tkk B
λ2 –frequency of deformation<|a|2> –amplitude of deformationp2 – size polydispersity, measurable by SANS or DLS
Farago et al. (1990)
Our Result: k /kBT = 0.24 @ 298K
Acknowledgments
Dobrin P. Bossev, Antonio Faraone, Steve Kline and Larry Kneller for their dedication and support during the experiments.
The entire NCNR staff for organizing the 2005 summer school.
6
Questions
Echo-point
0
2000
4000
6000
8000
1 104
1.2 104
-4 -2 0 2 4
1nsec_8A_19990609.dat1 cm apertures before solmain1 and after solmain2
solphase1 = 1.1296 A
Cou
nts/
35se
c
Phase Current (solphase2) (A)
y = m1*exp(-(m0-m2)*(m0-m2)/...13.7085159m1
9.1772e-050.56644m2 0.00429611.238m3 3.552e-050.23287m4
2.66367229.4m5 NA2539.1Chisq