Chemistry Reference
In-Depth Information
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Fig. 18 Comparison of experimental interfacial tension for PS/PMMA 10,000 at 199
C[
20
] with
the theory of Semenov [
33
]. The interaction parameter
a
=
w
/
u
was adjusted to 0.45
10
3
mol/
cm
3
(
u
is the effective monomer volume)
symmetric polymer/polymer system, as the temperature,
T
, approaches the critical
temperature,
T
c
, the interfacial tension and interfacial width behave as:
1
=
2
3
=
2
g /
T
c
r
e
(90a)
r
1
=
2
1
=
2
a
I
/
e
(91)
where
r
is the number of polymer segments and
e ΒΌ
T
)/
T
c
, with
T
c
the critical
point of demixing. Because for a symmetric system,
T
c
varies with molecular
weight as
T
c
/
(
T
c
r
,(
90a
) reduces to:
r
1
=
2
3
=
2
g /
e
(90b)
Thus, both interfacial tension
g
and interfacial width
a
I
were predicted to vary
with molecular weight to the 1/2 power, i.e., proportionally to the unperturbed
dimension of the polymer coil. Furthermore, the theory predicts the classical mean
field exponents of 3/2 and
1/2 for the dependencies of
g
and
a
I
, respectively, on
reduced temperature. Besides, Nose predicted a first order transition from a diffuse
to a relatively sharp interface that results in a change in the slope of the
g
versus
