microemulsion dynamics from neutron spin echo spectroscopy · microemulsion dynamics from neutron...
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Microemulsion Dynamics fromNeutron Spin Echo
Spectroscopy
Group DNCNR Summer School
2007
Sheila Khodadadi, Maggie Johnson, Jacob Tarver
Why study microemulsions?
1987 J. Huang et alPRL 59
Role of interfacetension vs bendingenergy
Fluctuations drivenby bending elasticity
2nm
How do we measure the dynamics?
0.05-15ns
SANS Structure Factor
Radius ~30A
Coherent scattering-collectivedynamics of surfactant shell
Contrast Match SLDs
solvents(D20, d-hexane)~6.1E-6
Surfactant (AOT) ~0.7E-6
NSE Spectrometer
Scatters from the nuclear interactionMeasured property-Final polarization
!
"# $%tF
!
tF"#3I
I is field Integral
Elastic Scatter
Data - Intensity for 1 detector
!
PZ =2A
Nup " Ndown
A
Also normalize to Carbon powder (Resolution)
Results on microemulsion
I(Q,t) atQ=.065,0.1,0.125
13 fourier times atλ=6A
!
I(Q,t)
I(Q,0)= exp "Deff (Q)Q
2t( )
Results-Elastic modulus
Q
Def
f
!
Deff (Q) = Dtr (Q) + Ddef (Q)
Extract Fit parameters R0, a2, Dtr,λ2
k=0.25kT
Conclusions
Were able to measure dynamics andelastic modulus for surfactant shell
Subsequent experiments have used spin-echo to study elastic modulus ofmembranes. (Bossev 2005 SS Invited Talk)
Acknowledgments
Antonio Faraone, Yamali HernandezMichihiro Nagao , Jason Gardner, Maikel
RheinstadterSummer School Instructors & PresentersJulie KeyserDAVE software http://www.ncnr.nist.gov/dave/download.hmtl
CHRNSTHANKS!