Measuring Self Diffusion Coefficients in Concentrated Polymer Solutions

1
Measuring Self Diffusion Coefficients in
Concentrated Polymer Solutions

• Joe Lott
• EMAC 474
• April 12, 2007

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1. Fluorescence Correlation Spectroscopy -
Introduced in the early 70's. - First
commercial instrument released in 1996 by
Zeiss. - Requires some type of fluorescent
chromophore in the system. - Polymers are
generally fluorescently labeled by attaching a
very small (lt1) amount of chromophores to the
backbone.
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1. Fluorescence Correlation Spectroscopy -
Introduced in the early 70's. - First
commercial instrument released in 1996 by
Zeiss. - Requires some type of fluorescent
chromophore in the system. - Polymers are
generally fluorescently labeled by attaching a
very small (lt1) amount of chromophores to the
backbone.
Experimental Setup1
4
1. Fluorescence Correlation Spectroscopy -
Introduced in the early 70's. - First
commercial instrument released in 1996 by
Zeiss. - Requires some type of fluorescent
chromophore in the system. - Polymers are
generally fluorescently labeled by attaching a
very small (lt1) amount of chromophores to the
backbone.
Experimental Setup1
Measurements2
- Observes a very small sample area. - Intensity
of the fluorescent signal is recorded as a
function of time.
Fluctuations in intensity are due to
Brownian motion of molecules into and out of the
area under observation
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1. Fluorescence Correlation Spectroscopy -
Introduced in the early 70's. - First
commercial instrument released in 1996 by
Zeiss. - Requires some type of fluorescent
chromophore in the system. - Polymers are
generally fluorescently labeled by attaching a
very small (lt1) amount of chromophores to the
backbone.
Data Analysis3 Autocorrelation Function N
average number of particles in the observation
volume w1 radius of focused beam w2 focal
depth along optical axis tD characteristic
decay time for diffusion Calculation of Dself
Experimental Setup1
6
1. Fluorescence Correlation Spectroscopy -
Introduced in the early 70's. - First
commercial instrument released in 1996 by
Zeiss. - Requires some type of fluorescent
chromophore in the system. - Polymers are
generally fluorescently labeled by attaching a
very small (lt1) amount of chromophores to the
backbone.
Experimental Results3
Experimental Setup1
Normalized FCS correlation functions of labeled
PS in toluene solutions having different
polymer concentrations (g/mL)
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1. Fluorescence Correlation Spectroscopy -
Introduced in the early 70's. - First
commercial instrument released in 1996 by
Zeiss. - Requires some type of fluorescent
chromophore in the system. - Polymers are
generally fluorescently labeled by attaching a
very small (lt1) amount of chromophores to the
backbone.
Experimental Results3
Experimental Setup1
Normalized FCS correlation functions of labeled
PS in toluene solutions having different
polymer concentrations (g/mL)
Diffusion coefficients of labeled PS in toluene
solutions as a function of polymer concentration,
showing predictions according to reptation theory
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2. Pulsed Gradient Spin-Echo NMR4 - Most
common method of measuring Dself - Convenient
noninvasive
Spin-Echo
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2. Pulsed Gradient Spin-Echo NMR4 - Most
common method of measuring Dself - Convenient
noninvasive
Spin-Echo
Pulsed Gradient Spin-Echo
Pulsed Gradient Spin-Echo -The two gradient
pulses are identical in amplitude, G, and width,
. The two gradient pulses are separated by a
time D and are placed symmetrically about the 180
degree pulse. -The function of the gradient
pulses is to dephase magnetization from spins
which have diffused to a new location in the
period D. These pulses have no effect on
stationary spins.
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2. Pulsed Gradient Spin-Echo NMR5
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2. Pulsed Gradient Spin-Echo NMR5,6
S/So exp-(Gigd )2 Di (D - d /3) S Signal Gi
diffusion coefficient in the i direction g
gyromagnetic ratio d width of gradient pulse D
time between gradient pulses
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2. Pulsed Gradient Spin-Echo NMR5,6
S/So exp-(Gigd )2 Di (D - d /3) S Signal Gi
diffusion coefficient in the i direction g
gyromagnetic ratio d width of gradient pulse D
time between gradient pulses
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References 1. Schwille, Peters, Haustein.
Fluorescence Correlation Spectroscopy.
Max-Plank-Institute for Biophysical
Chemistry. 2. Fluorescence Correlation
Spectroscopy http//imd-www.es.hokudai.ac.jp/gni
shi/fcs/fcs.html 3. Liu, R. Gao, X. Adams, J.
Oppermann, W. Macromolecules. 2005, 38, 8845. 4.
Basics of NMR http//www.cis.rit.edu/htbooks/nmr/
5. Price, W. Concepts Magn. Reson. 1997, 9,
299. 6. Arcos-Casarrubias, J. Olayo, R. J. Poly.
Sci. B. 2003, 41, 1605.
Questions?