Rigid Rod Probes of Concentrated Polymeric Solutions Randy Cush* & Paul Russo Louisiana State University Marrucci Symposium—74 th Society of Rheology Meeting October 15, 2002 -- Twin Cities *Current address: Syngenta, North Carolina You’re going to make it after all!
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Rigid Rod Probes of Concentrated Polymeric Solutions Randy Cush* & Paul Russo Louisiana State University Marrucci Symposium—74 th Society of Rheology Meeting.
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Rigid Rod Probes of Concentrated Polymeric Solutions
Randy Cush* & Paul RussoLouisiana State University
Marrucci Symposium—74th Society of Rheology MeetingOctober 15, 2002 -- Twin Cities
*Current address: Syngenta, North Carolina You’re going to make it after all!
DLS for Molecular Rheology of Complex Fluids:Prospects & Problems
+ + + Wide-ranging autocorrelators> 10 decades of time in one measurement!
– – – Contrast stinks: everything scatters, esp.in aqueous systems or most supercritical fluids, where refractive index matching cannot hide the matrix.
•Measure its diffusion in solutions of each polymer separately
•Random coil
•Polysaccharide
•Invisible in HvDLS
•Highly-branched
•Polysaccharide
•Invisible in HvDLS
•Rigid rod
•Virus
•Visible in HvDLS
Dextran
Ficoll
TMV
•Find polymer that should (???) “entangle”
BARELYBARELY
0 5 10 15 20 25 30 35 400
1
2
3
4
5
6
7
8
9
10
11
BothViscosity
sp/c
/dL
-g-1
c/g-dL-1
Dextran 670,000 Ficoll 420,000
As expected…
Seedlings
Sick Plants And close-up of mosaic pattern.
DIY farming--keeping the “A” in LSU A&M
TMV CharacterizationTMV Characterization
Sedimentation, Electron Microscopy and DLS
•Most TMV is intact.•Some TMV is fragmented
–(weaker, faster mode in CONTIN)
•Intact TMV is easy to identify –(stronger, slower mode in CONTIN)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
200
300
400
500D
t /10-8cm
2s-1
Dr /
s-110 L3
c/mg-mL-1
0
1
2
3
4
5
6
Rotation
Translation
Experiments are in dilute regime. TMV overlap (1/L3)
All measurements made at low TMV concentrations—no self-entanglement
Hv correlation Hv correlation functions for 14.5% functions for 14.5% dextran and 28% dextran and 28% ficoll with and ficoll with and without added without added 0.5 mg/mL TMV0.5 mg/mL TMV
The dilute TMV The dilute TMV easily “outscatters” easily “outscatters” either matrixeither matrix
Hydrodynamic Ratio—Effect of Matrix M at High Matrix Concentration
0 2 4 6 8 10 12 14 16 18 200
1
2
3
4
5
6
7
8
9DextranMWStudy_PR
Dro
t/Dtr
ans/
109 cm
-2
dextran MW/ 105 daltons
Effect of Dextran Molecular Weight—High Dextran Concentration (~ 15%)
10000 100000 1000000 1E71
10
100
DextranMWStudy_PR
-0.62 ± 0.04
Dro
t / s
-1
Dextran MW10000 100000 1000000 1E7
0.1
1
10
DextranMWStudy_PR
-0.72 ± 0.01
Dtr
ans/
10-9
cm
2 s-1
Dextran MW
TMV Translation TMV Rotation
Randy CushDavid Neau
Ding Shih
Holly Ricks
Jonathan Strange
Amanda Brown
Zimei Bu
Zuhal & Savas Kucukyavuz--METU
Seth Fraden—Brandeis
Nancy Thompson—Chapel Hill
NSF
Depolarized DLS—new opportunities in nanometer-scale rheology.
THE END
1 10 100
0.01
0.1
1
10
100
1000
10000
G' /
Pa
/ Hz
5% w/w 30% w/w 35% w/w 40% w/w
Behavior of Dextran Matrix
log
log
G’
Expected
Misalignment from thick polarizer in “active” part of detector train, exacerbated by tiny cells
used to squelch optical rotation & conserve TMV
shifted by thick polarizer element
correctly aligned scattered beam
Ld
1
1
3
3
3
L
L
L
1
1
2
2
2
dL
dL
dL
1
14
2
2
2
2
A
A
dLA
LC formation = 4/A2 5/dL2
Reduced # Density dL2/5
Doi-Edwards-Onsager Reference Volumes for Rods = number density = # of rods per unit volume
Thank you!
LSU
Randy Cush
David Neau
Ding Shih
Holly Ricks
Jonathan Strange
Amanda Brown
Zimei Bu
Zuhal & Savas Kucukyavuz--METU
Seth Fraden—Brandeis
Nancy Thompson—Chapel Hill
NSF
Conditions for use as a ProbeConditions for use as a Probe
•Is the TMV Probe Dilute?A TMV concentration of 0.5 mg/mL, well below the
theoretical overlap concentration, was chosen. See Figure 2.•Does dilute TMV overwhelm the matrix scattering?
At 0.5 mg/mL the TMV easily “outscatters” both matrices. See Figure 3.
•Is the probe compatible with the matrix?-Solutions stable months after preparation
-Angle dependent Hv SLS
-Dtrans goes up, not down (Figures 6 & 8)
Effect of Dextran ConcentrationEffect of Dextran Concentration
• The dependence of Drot and Dtrans upon added dextran is shown in Figure 4.
• The quotient Drot/Dtrans is plotted against viscosity in Figure 5. By combining both transport coefficients, each inversely proportional to viscosity in dilute solution, we can remove the effect of solution viscosity. • Figure 6 reveals like positive deviations from the Stokes-Einstein continuum expectation that diffusion be inversely proportional to viscosity (below 6.5%).
•Above 6.5% the deviations become greater for both Drot and Dtrans but in opposite directions
There once was a theorist from Francewho wondered how molecules dance.“They’re like snakes,” he observed, “As they follow a curve, the large onesCan hardly advance.”
D ~ M -2
P.G. de GennesScaling Concepts in Polymer Physics
Cornell University Press, 1979
de Gennes
OutlineOutline• Characterize the TMV
– Is it intact and behaving properly?
• Establish conditions for use of TMV as probe– Can the probe be dilute and still overwhelm the
matrix scattering?– Will the probe stay mixed with the matrix solutions
without aggregating?
• Show the effect of the dextran and ficoll matrices on TMV diffusion
An ear of corn has about as many kernels as TMVhas protein subunits (ca. 2130). The protein
subunits enfold a spiral-wound strand of RNA whichwill encode the next generation. TMV is more
extended than an ear of corn.
Effect of Ficoll ConcentrationEffect of Ficoll Concentration
• The dependence of Drot and Dtrans upon added dextran is shown in Figure 4.
• The quotient Drot/Dtrans is plotted against viscosity in Figure 7.
• Figure 8 shows slight like positive deviations from the Stokes-Einstein continuum expectation (below 11%).
• Above about 11% ficoll the deviation slowly becomes greater for Drot and slightly greater for Dtrans but in opposite directions
• Figure 9 compares TMV behavior in ficoll to that in dextran.
• Below 6.5% dextran the diffusion of the rodlike TMV probe is controlled mostly by viscosity.
• Above 6.5% dextran a sharp transition suggests topological constraint for TMV rotation while translation is not much affected.
• The transition is more gradual in ficoll.• The TMV probe senses something different for
linear vs. highly branched polymers in solution.• Looks good for topological models!
Alternate Conclusion?• The systems studied so far place (impossibly?) strict
demands on geometric & polarization alignment. – Revised polarization placement– Difficult zero angle measurements requiring even more
TMV
• New systems must be studied:– TMV is OK – Dextran/Ficoll must go!
• Depolarized probe diffusion has the potential, as yet unrealized, to assess strength of hydrodynamic vs. topological effects.
To Do
Get Cush to estimate the total number of TMV’s he produced.
Slopes of intrinsic viscosity plot don’t meet the 0.5 rule.
What has Deutch & Pecora to do with Dtrans vs. M?
What does regular viscosity have to say about M-dependence?
At what concentration was that M-dependent stuff done?
Entanglement in solution?Entanglement in solution?
To isolate spaghetti in "solution" with a fork is To isolate spaghetti in "solution" with a fork is difficult: hydrodynamic interactions interfere difficult: hydrodynamic interactions interfere with entanglement. After solvent is drained to with entanglement. After solvent is drained to obtain a "melt" the entire blob is easily handled. obtain a "melt" the entire blob is easily handled.