Biomedical Engineering Reference
In-Depth Information
10.00
8.00
6.00
4.00
2.00
0.00
1.00
3.00
5.00
7.00
pH
9.00
11.00
13.00
Figure 5.9
Water contents as a function of pH for the cross-linking chitosan/poly(oxypropylene glycol) semi-IPN hydro-
gels at equilibrium swollen state. Solid line: total water; dashed line: bound water.
medium and the swelling equilibrium is established faster at neutral or basic medium
than at acidic medium. In addition, the different hydrogel compositions have a certain
effect on the swelling performance. For example, in chitosan/PEG and chitosan/PVA
semi-IPN hydrogels, the bound water decreases as the percentage of chitosan decreases
because of the weaker water-binding ability of the -OH group compared to the -NH
3
group due to its fewer polar moieties [23].
80
70
60
50
40
pH
=
13
30
20
10
pH
=
1
0
0 0 100 150 200 250
Time (min)
300 350 400 450 500 550
Figure 5.10
Degree of swelling as a function of time for chitosan/poly(oxypropylene glycol) (solid) and chitosan (blank)
hydrogels after repeated changes of pH between 1 and 13.
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