Here is a nice example of scaling: 3 different types of polymers, all normalized
sround the entanglement molecular weight and viscosity at that molecular weight.
From Rubinstein & Colby
Polymer Physics
The best experiments do not match the reptation prediction exactly.
From Rubinstein & Colby
Polymer Physics
What has this got to do with our creep compliance plot?
12 decades of time!!!???
In a mechanical experiment???
From Rubinstein & Colby
Polymer Physics
From Rubinstein & Colby
Polymer Physics
It is easier for a camel to pass through the eye of a needle
than for an octopus to escape a fishnet.
From Rubinstein & Colby
Polymer Physics
Can you think of an
experiment?
No one knows if reptation really happens in solutions; these
diffusion results from an obscure group in Baton Rouge
suggest not.
1
-7
2
Ds / 10 cm s
-1
10
0.1
10000
Mw / Da
100000
Figure 1: Diffusion of fluorescently tagged dextran in unlabeled d
extran matrix of Mw = 2,000,000 Da. No Matrix (), 5% w/w Matrix (■),
10% w/w Matrix (), 15% w/w Matrix (), 20% w/w Matrix (○), and 25% w/w ().
We are putting probe diffusion to work. This molecular
weight distribution was obtained without GPC, without
AF4, without any separation at all.
12
10
% Amplitude
8
6
4
2
0
10000
M
100000
Figure 5. Representative spectra calculated by CONTIN and chosen by the user
showing the detection of FD20 and FD70 in a mixture. The weight percent of
the matrix solutions was 0.25. Spurious peaks at low and high M not shown.
Molecules were just put under a “speed gun” as
they diffuse around In a constraining solution.
GPC is actually LESS effective in this case.
1.0
FD20
FD70
Relative Concentration
0.8
MIX
0.6
0.4
0.2
0.0
10000
100000
M / g mol
-1
Figure 6: GPC-MALS separation of FD20 and FD70 (circles; two different
injections are shown). Also shown are individual runs for FD20 (-) and FD70 (+).
Rheology plays a role in figuring out why our “nonseparation” method doesn’t work even better.
10
20 Hz
G' / Pa
10 Hz
1
5 Hz
0.1
0.01
0.00
2 Hz
0.05
0.10
0.15
0.20
0.25
w
Figure 7: Illustration of the change of G′ over the range of dextran matrix
concentrations at oscillation frequencies 2 Hz (■), 5 Hz (●), 10 Hz (▲), 20 Hz ().
This figure demonstrates the absence of a rheological
plateau modulus in the measured frequency range for
the matrix dextran.
100
G' / Pa
10
1
0.1
0.01
1
10
100
 / Hz
Figure 7: Example of storage modulus, G′, as a function of frequencies for different
dextran matrix concentrations: w = 5% (■), 10%(▲), 15%(), 20%(○), and 25%()