Chemistry Reference
In-Depth Information
25
25
3
w(F)
PDI
w(F)
log rw
5.5
2.5
20
20
4.5
2
15
15
3.5
1.5
10
10
2.5
1
5
5
1.5
0.5
0
0
0
0.5
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.35
0.4
0.45
0.5
0.55
0.6
0.65
F
F
Figure 11.
Weight average chain length (r
w
) and polydispersity ind
e
x (PDI) of a binary model copolymer as a function of
comonomer composition. Model parameters:
r
n
¼
500, F
¼
0
:
5,
r
1
r
2
¼
1.
and average weight average chain lengths
(
Figure 12 shows a model plot for three
site types. These results are only qualita-
tive; they represent trends, not actual
values, since the representation of TREF
profiles directly from Stockmayer's distri-
butions is not accurate enough for quanti-
tative calculations.
R
w
) with the equation,
X
n
R
w
ðFÞ¼
1
D
w
j
ðFÞm
j
r
w
j
ðFÞ
(23)
j
¼
where
D
w
j
(F) is the fraction of polymer
with comonomer composition
F
made on
site type j, calculated as:
Long Chain Branching Distribution
Z
F
þ
D
F
Figure 13 shows the predicted distributions
of chain length and comonomer composi-
D
w
j
ðFÞ¼
w
j
ðFÞ
d
F
(24)
F
9
7
6
6
Log M
w
TREF
5.8
5
5.6
8
4
6
5.4
5.2
3
5
2
4.8
7
4.6
1
W(F)
log Rw
5
4.4
0
4.2
6
30
40
50
60
70
80
90
100
110
Temperature ºC
4
5
3
4
2
3
1
2
0
1
0
-1
0.5
0.6
0.7
0.8
0.9
F
Figure 12.
CCD-R
w
profile for a model three-site copolymer. The theoretical plot was adjusted to resemble the
experimental plot (insert) but this representation is only qualitative.
