Chemistry Reference
In-Depth Information
2.5
2
1.5
1
0.001
0.01
0.1
1
concentration, c/g cm
-3
Figure 5.21
A plot for the chain expansion factor for polybutadiene from the work of
Graessley.
35
10
9
10
7
M
3.4
10
5
10
3
M
0
10
1
M
C
10
-1
10
2
10
3
10
4
10
5
10
6
molecular weight /gmol
-1
Figure 5.22
A schematic of the log of the viscosity multiplied by the ratio of friction
coefficients versus the log of the molecular weight.
weight M
C
the viscosity shows a greater dependence on molecular weight being
proportional to M
3.4
. This is shown schematically in Figure 5.22.
This change has been associated with the onset of entanglements between the
chains. These restrict the polymer motion and the relaxation time. Beuche
27
