Chemistry Reference
In-Depth Information
3
12
XL functionality,
Fi g u re 7. 8:
The effect of cross-link functionality on 2
C
2
/2
C
1
.
Fi g u re 7. 9:
Sketch of an interchain entanglement.
Vilgis and Erman
161
that the constraint models and slip-link models have
much in common, (iv) elucidating the effects of cross-link functionality and
degree of cross linking, (v) exploring a variety of elastomeric polymers, par-
ticularly those having very different values of the plateau modulus,
162
and (vi)
generalizing rubber-elasticity models to include viscoelastic effects as well.
For purposes of illustration, it is useful to consider some studies of Op-
permann and coworkers
163,
164
on end-linked PDMS networks of different
functionalities, since some of the aforementioned issues arose in the anal-
ysis of their experimental data.
96
Here, studies of the small-strain shear
modulus of end-linked PDMS networks with pentafunctional junctions
were carried out as a function of network chain density. The data agree
with predictions of the molecular theories at larger values of the chain or
junction densities. At lower junction densities however the measured
