Chemistry Reference
In-Depth Information
The temperatures of the reactions and the nature of the aluminum compounds are the most
important synthetic variables [
367
].
On the other hand, many other graft copolymerizations by cationic mechanism suffer from low
grafting efficiencies. They are also often accompanied by large formations of homopolymers. Use,
however, of living cationic processes appears to overcome this drawback. An illustration of this can
be another preparation of a graft copolymer of polyisobutylene on a polystyrene backbone [
413
]:
BCl
3
isobutylene
CH
2
Cl
O
BCl
3
O
x
O
O
9.6.8 Miscellaneous Graft Copolymerizations
In a rather interesting reaction, ethylene oxide can be graft-copolymerized with nylon 6,6 [
406
].
Formation of the graft copolymer greatly enhances flexibility of the material, while the high melting
point of the nylon is still maintained. Thus, nylon 6,6 that contains as much as 50% by weight of
grafted poly(ethylene oxide) still melts at 221
C and has an apparent
40
C. It also
maintains flexibility and other useful properties over a wide range of temperatures [
406
]:
T
g
below
O
O
N
N
6
4
H
O
O
H
An entirely different procedure can be used to form graft copolymers by a step-growth polymeri-
zation [
347
]. Formaldehyde is condensed with either phenol,
-nonyl phenol and the resin
is attached to either nylon 6, nylon 6,6, nylon 6,10, or nylon 11 backbones. Initially, the formaldehyde
p
-cresol, or
p
