Chemistry Reference
In-Depth Information
d
½
M
1
=
d
½
M
2
=
d
½
M
3
¼½
M
1
f½
M
1
þ½
M
2
=r
12
þ½
M
3
=r
13
g
=½
M
2
r
21
=r
12
f½
M
1
=r
21
þ½
M
2
þ½
M
3
=r
23
g
=½
M
3
r
31
=r
13
f½
M
1
=r
31
þ½
M
2
=r
32
þ½
M
3
g
It is claimed that this
terpolymerization composition equation
is often in good agreement with
experimental results. Other, more complicated equations also exist, but apparently they yield results
that are similar to those obtained from the above shown expression [
94
,
149
].
One example of other equations is an early theoretical relationship for terpolymerization that was
written by Alfrey and Goldfinger [
150
].
a
b
¼
A½A=ðr
31
r
21
ÞþB=ðr
21
r
32
ÞþC=ðr
31
r
23
Þ½AþB=r
12
þC=r
13
B½ðA=ðr
12
r
31
ÞþB=ðr
12
r
32
ÞþC=ðr
32
r
13
Þ½BþA=r
21
þC=r
23
:
a
c
¼
A½A=ðr
31
r
21
ÞþB=ðr
21
r
32
ÞþC=ðr
31
r
23
Þ½AþB=r
12
þC=r
13
C½A=ðr
13
r
21
ÞþB=ðr
23
r
12
ÞþC=ðr
13
r
23
Þ½CþA=r
13
þB=r
32
where
C
are the quantities of the monomer in the feed system. Needless to say, a copolymerization of four or
even more monomers becomes progressively more difficult to treat rigorously.
a
,
b
, and
c
are the quantities of each monomer found in the resultant terpolymer and
A
,
B
, and
3.8 Allylic Polymerization
Compounds possessing allylic structures polymerize by free-radical mechanism only to low
molecularweight oligomers. In some cases the products consist mostly of dimers and trimers. The
DP for poly(allyl acetate), for instance, is only about 14. This is due to the fact that allylic monomer
radicals are resonance-stabilized to such an extent that no extensive chain propagations occur.
Instead, there is a large amount of chain transferring. Such chain transferring essentially terminates
the reactions [
151
]. The resonance stabilization can be illustrated on an allyl alcohol radical:
OH
OH
The hydrogen transfer takes place from the allylic hydrogen, as shown on allyl acetate:
O
O
+
RH
R
+
O
O
O
O
