Chemistry Reference
In-Depth Information
experiments. For the remaining parameters, the following values were assumed for
solvent mixture 1:
w
AP
¼
0
:
427 K
p
A
¼
0
:
1
(66)
and for solvent mixture 2:
w
AP
¼
0
:
671 K
p
A
¼
0
:
05
:
(67)
The theoretical frameworks were executed for the calculations of the distribu-
tions in the intermediate and in the final fractions. In Fig.
16
, the calculated mass-
average chemical compositions were compared with the experimental data obtained
by the one-direction fractionation [
75
]. Using the solvent mixture 1, the mass-
average chemical composition decreases with increasing number of fraction. Using
the solvent mixture 2, this property increases with increasing number of fraction.
The reason for this finding is the sign of the parameter, g
A
, which is positive for the
solvent mixture 1 and negative for the solvent mixture 2. The agreement between
the experimental and calculated data is much better for the fractionation in the
solvent mixture 1 than in the solvent mixture 2, especially for the fractions with a
high fraction number. During the experiments [
75
] using the solvent mixture 2,
evaporation of the solvent was observed. This effect is not taken into account in the
theoretical calculations.
In Fig.
17
, the experimental [
75
] and calculated number-average segment num-
bers are compared. According to the SPF mechanisms, the copolymers having the
highest molecular weight will preferentially be in the first fractions, independent of
the chosen solvent mixture. Except for the fractions having a very high molecular
weight, the proposed theoretical framework is able to model
the experiment
0,35
0,30
0,25
0
2
4
6
8
10
12
14
number of fraction
Fig. 16 Comparison of experimental (
symbols
)[
75
] and calculated (
lines
) mass average chemical
compositions in every fraction after performing a one direction fractionation using two different
solvents:
circles and solid line
solvent mixture 1;
squares and broken line
solvent mixture 2
