Chemistry Reference
In-Depth Information
The effectiveness of random copolymerization in depressing crystalliza-
tion and melting point can be further demonstrated by the polymer
3
.
21
(Jackson & Kuhfuss, 1982). In comparison to the polymer
3
.
19
, the poly-
mer
3
.
21
has an even lower melting point (330
◦
C) even though the extent
of the substitution is lower by 25%.
O
O
O
O
O
O
C
C
O
O
C
C
3
.
21
0.25
0.75
Similarly, copolymerization of a certain amount of 4-hydroxybenzoic acid
(HBA) with phenyl-1,4-hydroquinone and terephthalic acid also gives rise
to a remarkable decrease in the melting point. The general structural for-
mula and the melting points of the copolymers with different HBA content
are given respectively by
3
.
22
and Table 3.6. In this particular case, the
incorporation of 20 mol % of HBA into the polymer
3
.
19
has resulted in
a polymer with a melting point as low as 229.
O
O
O
O
O
C
C
O
C
3
.
22
x
y
shown below. The only difference in structure of these two polymers is that
in
It is interesting to make a comparison of the polymer
3
.
19
with
3
.
23
3
.
19
the phenyl substituent is on the
O
O
O
O
C
C
m.p. 278
◦
C
3.23
hydroquinone moiety while in
(Harris, 1981) the substitution is on
the terephthalic moiety. However, the difference in melting point of the two
is a remarkable 343
◦
C to 278
◦
C. Because of the very high similarity in
3
.
23
