Chemistry Reference
In-Depth Information
Al(C2H5)2H
C
2
H
5
Al
C
2
H
5
TiCl
4
(TiC
3
,VOC
l
3
)
n
Another example is formation of graft copolymers of formaldehyde with starch, dextrin, and poly
(vinyl alcohol) [
366
,
367
]. This procedure is also carried out in two steps. Potassium naphthalene is
first reacted with the backbone polymer in dimethylsulfoxide. The formaldehyde is then introduced in
gaseous form to the alkoxide solution.
A similar reaction can be used to form graft copolymers of poly(ethylene oxide) on cellulose
acetate [
391
]. Poly(ethylene oxide) can also be grafted to starch. For instance, a preformed polymer
[
392
] terminated by chloroformate end groups can be used with potassium starch alkoxide:
O
O
O
starch
O
K
+
Cl
O
O
Cl
n
O
O
O
starch
O
O
O
Cl
n
The products are water-soluble. The efficiency of the coupling process, however, decreases with
an increase in the DP of poly(ethylene oxide).
Lithiated polystyrene reacts readily with halogen-bearing polymers like polychlorotrifluor-
oethylene [
411
]. This can be utilized in formation of graft copolymers. The reactions can be
conducted in solutions as well as in preparations of surface grafts on films [
411
].
An example of a cationic grafting reaction is formation of graft copolymers of polyisobutylene on
polystyrene backbones [
393
]. Polystyrene is chloromethylated and then reacted with aluminum
bromide in carbon disulfide solution. This is followed by introduction of isobutylene:
Cl
O
+
Cl
