Chemistry Reference
In-Depth Information
Table 6.3
Properties of copolymers having different molecular weight
Tensile strength
(kgf/cm
2
)
Sample
Elongation Contact angle (
) Water absorption (%) Grafting (%)
1
a
80
0.54
66
1.4
650
2
a
90
0.52
65
2.6
550
3
a
86
0.42
65
7.0
175
4
b
410
3.00
68
0.9
690
5
b
390
2.64
65
1.6
500
6
b
365
2.20
65
2.5
260
7
c
293
2.20
69
1.2
720
8
c
270
1.66
68
1.5
400
9
c
266
1.50
68
1.6
300
PMMA
d
507
3.90
72
0.8
-
a
Backbone polymer dextran D3 (
M
w
196,000)
b
D2 (
M
w
61,000)
c
D1 (
M
w
9,000)
d
Sample isolated from copolymer
The relation between elongation and grafting (%) was similar to the above relation.
The copolymer with the backbone polymer dextran of
M
w
61,000 (D2) was superior
to others with regard to elongation.
The contact angle of these copolymers was lower than for PMMA, but a
systematic effect of grafting (%) and the backbone polymer dextran
M
w
was not
observed.
6.2.5.6 Characteristic Properties of Dextran-MMA Graft Copolymers for
Biomaterials
Figure
6.10
shows the IR absorption spectra of dextran-MMA copolymer, the
starting material dextran and side chain PMMA. The spectrum of the copolymer
has some characteristic absorption bands, e.g., the bands at around 3,410 cm
1
,
1,725 cm
1
and 1,000-1,150 cm
1
are due to O-H stretching vibrations of dextran,
the carbonyl group of PMMA and the pyranose ring of dextran, respectively.
Comparison of this spectrum with those of dextran and PMMA shows that the
spectrum of dextran alone has no absorption band at 1,720 cm
1
due to the
stretching vibration of C
O, and that the spectrum of PMMA alone has no
absorption band at around 3,410 cm
1
.
Figure
6.11
shows DSC (differential scanning calorimetry) curves for the
dextran-MMA copolymer, having grafting of 230 %, and for the starting material
dextran and the side chain PMMA. The glass transition temperature (
T
g
), which
appears as a step or a small kink in the DSC curve, is observed near 199 and 127
C
for the copolymer and PMMA, respectively. For dextran, a broad and strong
endothermic peak (similar to the thermal features of starch having a-linkages
[
32
]) is observed in the range 50-200
C (peak temperature at 120
C) and the
complicated decomposition of the dextran occurs at temperatures above 220
C. For
the copolymer, the endothermic peak relating to the molecular constitution of
ΒΌ
