Chemistry Reference
In-Depth Information
10
4
s
1
with dextran D1,
reaction time. The value of
k
0
obtained was 6.5
10
4
s
1
with D3. The molecular weight of
these dextrans oxidized by Ce
4+
and that of each starting dextran were the same.
The order for the rates of consumption of Ce
4+
by dextran was D1
10
5
s
1
with D2 and 3.2
5.0
D3.
Thus, for lower molecular weights, the rate of oxidation increases moderately. The
result is consistent with that for grafting (%) (cf. Fig.
6.5
).
From the above results, it was concluded that graft polymerization proceeds
under the influence of the molecular weight of the backbone polymer dextran.
>
D2
>
6.2.3 Polymerization Kinetics
6.2.3.1 Theory
Ceric ions complex reversibly with alcohols and glycols.
The disproportion of the
complexes is the rate-determining step of the reaction [
29
-
31
]. Mino and
Kaizerman have also shown that the oxidation-reduction proceeds via free radicals,
which are capable of initiating vinyl polymerization [
1
]. The elementary reactions
considered from experiment are as follows:
Initiation
K
k
1
Ce
4
þ
!
Ce
3
þ
þ
!
þ
D
complex
D
(6.1)
k
2
D
þ
M
!
DM
(6.2)
k
3
D
0
þ
D
þ
M
!
M
(6.3)
Propagation
k
4
DM
n
DM
þ
M
!
(6.4)
Termination
k
5
DM
n
þ
M
!
copolymer
þ
M
(6.5)
k
6
DM
n
þ
DM
n
!
copolymer
(6.6)
