Chemistry Reference
In-Depth Information
Fig. 4 Breakdown of the
composition dependence of
w into the contributions
resulting from the two steps
of dilution (cf. Fig.
1
and (
32
),
a 1.599, n 0.398, and
zl 1.074) for the CH/
PVME 28 system at 35
C
4
a
(1-
nj
)
2
3
2
1
0
-1
-2
-
zl
(1+2
j
)
-3
0.0
0.2
0.4
0.6
0.8
1.0
j
CH
PVME 28
1.5
Fig. 5 Interrelation between
the leading parameters of
(
32
).
Closed symbols
data
from
A
2
(M) [
39
];
open
symbols
data from w(
'
)[
23
].
Each symbol stands for a
different polymer/solvent
system, the polymers being
PS, PMMA, polyisobutylene,
and PDMS
1.0
0.5
0.0
0.0
0.5
1.0
a
1.5
manner: Both terms can be split into their enthalpy and entropy parts, as will be
shown later.
Another point of view on the contributions of the two terms of (
32
) deserves
special attention. Namely, the expectation according to the present approach that
their leading parameters, a and z, should not be independent of each other.
The reason for this surmise lies in the fact that contact formation and conforma-
tional relaxation share the same thermodynamic background, i.e., the effects of the
conformational relaxation of the components should strongly correlate with the
effects of contact formation, as discussed in Sect.
2
.
The results shown in Fig.
5
demonstrate that there indeed exists such a general
interrelation, where each data point represents a certain system and temperature.
The results of this graph demonstrate the consistency of the approach because the
data [
39
] obtained from the evaluation of the molecular weight dependence of
A
2
(cf. Fig.
2
) and from the composition dependence of w(
'
) (an example [
40
] is shown
in Fig.
3
) lie on the same line [here zl = (0.957
0.5)], despite the
fundamentally different experimental methods used for their determination. For the
common representation of the data, the z values reported in table 2 of [
39
] were
multiplied by
0.00027)
(a
0.5 (i.e., l was set at 0.5), which is permissible for sufficiently large
